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  • Engineering  (2,961)
  • Cell & Developmental Biology  (2,509)
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  • 1995-1999  (7,247)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 377-386 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Apoptosis in cells of different lineages is restrained by survival signals which depend upon cell-to-cell communication. The aim of this study was to determine whether colonic cells deprived of crypt ambient are doomed to die prior to their normal chronological demise. Apoptosis was studied in rat whole colonic tissue, in isolated intact crypts, and in colonic cell populations collected from the crypt axis at different stages of proliferation and differentiation. In a number of experiments, cell harvest was performed in the presence of either a tetrapeptide (YVAD-CMK) inhibitor of interleukin-1β-converting enzyme (ICE), or tyrphostin A25, a protein tyrosine kinase inhibitor, or sodium-orthovanadate, a phosphatase inhibitor. DNA fragmentation was assessed by electrophoretic and nonisotopic-labeling procedures. The ultrastructure of colonic tissue specimens and isolated cells was examined by transmission electron microscopy. Apoptosis in whole colonic tissue and in isolated crypts was confined predominantly to cells resident in the upper crypt regions. In contrast, extensive apoptotic death was observed in isolated colonic cells, irrespective of their developmental stage and positional hierarchy within the crypt continuum at harvest time. An apoptotic gradient, however, was evident. Exposure to YVAD-CMK resulted in a marked decrease in the number of apoptotic cells. Treatment with tyrphostin A25 caused a sharp rise in the apoptotic index; conversely, vanadate significantly impeded apoptosis. Cumulatively, these results indicate that disordered intercellular communication provokes unscheduled ICE-mediated apoptosis of colonocytes, and that local signals along the crypt continuum control both the reprieve from death and the timely demise of distinct colonic cell populations. Attenuation of tyrosine phosphorylation may be a contributory event in the acquisition of the apoptotic phenotype. J. Cell. Physiol. 177:377-386, 1998. © 1998 Wiley-Liss, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 518-524 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: No abstract.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 525-534 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: No abstract.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 575-584 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of hsp27 as an inhibitor of actin polymerization was considered in the context of the actin cytoskeleton and its relationship with focal adhesion formation. The aim of this study was to evaluate the potential effects of hsp27 on focal adhesion formation as a relevant biological consequence of actin stress fiber formation. When hsp27 was overexpressed in stably transfected cells, cell attachment was delayed and recovery of disrupted stress fibers and focal adhesions was limited. In ROS 17/2.8 cells, heat shock caused the reversible disruption of stress fibers and focal adhesions. The loss of stress fibers and focal adhesions was associated with reduced phosphotyrosine on the focal adhesion kinase (FAK). Microinjection of recombinant 6-His hsp27 and phosphorylated 6-His hsp27 was used to demonstrate that nonphosphorylated hsp27 prevented the recovery of stress fibers and focal adhesions. These results provide in vivo evidence that hsp27 acts as an inhibitor of actin polymerization that can alter cellular interactions with extracellular environments by perturbation of stress fibers, and subsequently focal adhesions. J Cell Physiol 177:575-584, 1998. © 1998 Wiley-Liss, Inc.
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  • 5
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Hepatocytes entrapped in collagen gel and cultured in serum-free conditions survived longer than cells cultured on plastic (5 days vs. 3 weeks), showed fewer signs of early cell senescence (no increase in c-fos oncoprotein expression), and maintained the expression of differentiated hepatic metabolic functions over a longer period of time. Cells cultured in collagen gels retained their ability to respond to hormones. The insulin-stimulated glycogen synthesis rate remained fairly constant during 18 days in culture (between 5.4 ± 0.37 and 9 ± 2.7 nmol glucose/h/μg DNA). Collagen-cultured hepatocytes recovered glycogen stores to levels similar to those found in liver, or in hepatocytes isolated from fed rats. Urea synthesis from ammonia remained stable for more than 2 weeks (average value, 23 ± 4 nmol urea/h/μg DNA). The rate of albumin synthesis in collagen-entrapped cells was maintained above the day-1 level during 18 days in culture. Cells showed high levels of glutathione (GSH) (1,278 ± 152 pmol/μg DNA). Biotransformation activities CYP4501A1, CYP4502A2, CYP4502B1, and CYP4503A1 remained fairly stable in collagen-cultured hepatocytes. CYP4502E1 and CYP4502C11 decreased but were still measurable after 18 days. After 4 days in culture, GST activity returned to levels observed in isolated hepatocytes. In contrast with plastic cultures, cells responded to CYP450 inducers (methylcholanthrene for CYP4501A1, CYP4501A2, and gluthatione-transferase, and ethanol for CYP4502E1) for more than 2 weeks. CYP4501A1, CYP4501A2, and glutathione-transferase A2 (GST A2) induction was preceded by an increase in specific mRNA, while the effects on CYP4502E1 seemed to be at a posttranslational level. Analysis of the expression of relevant hepatic genes by reverse Northern and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that culturing hepatocytes in collagen gels results in a sustained higher expression of key liver transcription factor genes DBP, C/EBP-α and -β, and HNF-1 and -4, as well as specific liver enzyme genes (phosphoenol pyryvate carboxykinase, and carbamoylphosphate-synthetase I). J Cell Physiol 177:553-562, 1998. © 1998 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 535-552 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The viral Crk oncogene (v-Crk) is known to induce sarcomas in chicken and its cellular homologs c-Crk I, c-Crk II, and Crk-like (CRKL) have been implicated in many signal transduction events. These include cell differentiation, cell migration, and the induced nonresponsiveness of T-cells to stimulation of the T-cell receptor (TCR), a state known as anergy. CRKL is also the most prominent substrate of the Bcr-Abl oncoprotein which causes human chronic myelogenous leukemias (CML). The modular composition of the Crk family adapters which largely consist of Src homology (SH2 and SH3) domains has prompted an intensive search for physiological and pathological upstream and downstream signalling partners which selectively bind to these adapters. Upstream proteins include various receptors and large multisite docking proteins, while several protein kinases and guanine nucleotide release proteins (GNRPs) have been suggested to function downstream of c-Crk and CRKL. Most Crk/CRKL SH2- and SH3-binding proteins contain several docking sites with considerable sequence similarity. Thus the binding requirements of Crk/CRKL SH2 and SH3 domains are now well defined, providing a basis for the design of small inhibitory molecules to block the function of these adapter proteins. The enzymatic cascades activated through Crk family adapters are only partially known, but stress kinases (SAPKs/JNKs) and the GTPase Rap1, as well as the B-Raf isoform of the Raf protein kinases, are affected in some systems. Several yet unidentified, highly selective Crk interacting proteins detectable in specific cell types remain to be studied. More detailed analyses of the enzymatic activities triggered through Crk-type adapters will also be crucial to fully define the signalling pathways controlled by this protein family. J Cell Physiol 177:535-552, 1998. © 1998 Wiley-Liss, Inc.
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  • 7
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have previously described a specific, saturable receptor for rat collagenase-3 in the rat osteosarcoma cell line, UMR 106-01. Binding of rat collagenase-3 to this receptor is coupled to the internalization and eventual degradation of the enzyme and correlates with observed extracellular levels of the enzyme. In this study we have shown that decreased binding, internalization, and degradation of 125I-rat collagenase-3 were observed in cells after 24 h of parathyroid hormone treatment; these activities returned to control values after 48 h and were increased substantially (twice control levels) after 96 h of treatment with the hormone. Subcellular fractionation studies to identify the route of uptake and degradation of collagenase-3 localized intracellular accumulation of 125I-rat collagenase-3 initially in Golgi-associated lysosomes and later in secondary lysosomes. Maximal lysosomal accumulation of the radiolabel and stimulation of general lysosomal activity occurred after 72 h of parathyroid hormone treatment. Preventing fusion of endosomes with lysosomes (by temperature shift, colchicine, or monensin) resulted in no internalized 125I-collagenase-3 in either lysosomal fraction. Treatment of UMR cells with the above agents or ammonium chloride decreased excretion of 125I-labeled degradation products of collagenase-3. These experiments demonstrated that degradation of collagenase-3 required receptor-mediated endocytosis and sequential processing by endosomes and lysosomes. Thus, parathyroid hormone regulates the expression and synthesis of collagenase-3 as well as the abundance and functioning of the collagenase-3 receptor and the intracellular degradation of its ligand. The coordinate changes in the secretion of collagenase-3 and expression of the receptor determine the net abundance of the enzyme in the extracellular space. J Cell Physiol 177:563-574, 1998. © 1998 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 585-592 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of metabolic inhibitors on nontransferrin bound iron transport by K562 cells was investigated. Incubation with 1 μM rotenone, 10 μM antimycin, or 0.5 mM 2,4-dinitrophenol effectively reduced ATP levels by ∼50%. Both the rate and extent of Fe+3 uptake were impaired in ATP-depleted cells, which display a reduced Vmax for uptake. K562 cell ferrireductase activity was also lowered by metabolic inhibitors, suggesting that the apparent energy requirements for transport reside in the reduction of Fe+3 to Fe+2. However, ATP depletion was found to inhibit the rate and extent of Fe+2 uptake as well. Thus, the transbilayer passage of Fe+2 and/or Fe+3 appears to be an energy-requiring process. These features possibly reflect properties of the transport mechanism associated with a recently identified K562 cell transport protein, called SFT for “Stimulator of Fe Transport,” since exogenous expression of its activity is also affected by ATP depletion. J Cell Physiol 177:585-592, 1998. © 1998 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 593-605 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Clusterin (ApoJ) is an extracellular glycoprotein expressed during processes of tissue differentiation and regression that involve programmed cell death (apoptosis). Increased clusterin expression has also been found in tumors, however, the mechanism underlying this induction is not known. Apoptotic processes in tumors could be responsible for clusterin gene activation. Alternatively, oncogenic mutations could modulate signal transduction, thereby inducing the gene. We examined the response of the rat clusterin gene to two oncogenes, Ha-ras and c-myc, in transfected Rat1 fibroblasts. While c-myc overexpression did not modify clusterin gene activity, the Ha-ras oncogene produced a seven to tenfold repression of clusterin mRNA; this down-regulation was also observed in the presence of c-myc. Since no induction of the clusterin gene was observed by the two oncogenes, we tested the alternative mechanism involving apoptosis. Growth factor withdrawal induced apoptosis, as shown by DNA degradation and micronuclei formation in the floating cells. Concomittantly we observed a three to tenfold increase in the amount of clusterin mRNA in the adhering cells of Rat1 and the c-myc transformed cell lines, and a weaker induction in the Ha-ras transformed cell line. On the basis of our results, we suggest that clusterin gene induction in the vital cells is produced by signaling molecules that are generated by the apoptotic cells. We conclude that apoptotic processes, not oncogenic mutations, are responsible for increased clusterin expression in tumors. J Cell Physiol 177:593-605, 1998. © 1998 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 618-627 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We previously reported that the enterocytic differentiation of human colonic Caco-2 cells correlated with down-regulation of fibronectin (FN) and laminin (LN), two extracellular matrix components interacting with cell surface integrin receptors. We now investigated whether Caco-2 cell differentiation was associated with alterations in integrin signaling with special interest in the expression and activity of focal adhesion kinase (FAK) and mitogen-activated protein (MAP) kinase. The differentiation of Caco-2 cells was associated with: (1) down-regulation of β1 integrin expression at the mRNA and protein levels; (2) increased FAK expression together with decreased FAK autophosphorylation; (3) decreased FAK's ability to associate with PI3-kinase and pp60c-src; and (4) increased MAP kinase expression along with decreased MAP activity. In addition, we show that FAK and MAP kinase belong to distinct integrin signaling pathways and that both pathways remain functional during Caco-2 cell differentiation since the coating of differentiating cells on FN and LN but not on polylysine increased the tyrosine phosphorylation of FAK and of its endogenous substrate paxillin, and stimulated MAP kinase activity. In conclusion, our results provide evidence that FAK and MAP kinase, two signaling molecules activated independently by β1 integrins in Caco-2 cells, undergo alterations of both expression and activity during the enterocytic differentiation of this cell line. J Cell Physiol 177:618-627, 1998. © 1998 Wiley-Liss, Inc.
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  • 11
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Salivary glands contain two major epithelial cell types: acinar cells which produce the primary salivary secretion, including amylase, and ductal cells which reabsorb electrolytes but also secrete kallikrein. Here we investigated salivary acinar cell differentiation in vitro using the activity of the salivary amylase and tissue kallikrein promoters as markers of acinar cell and ductal cell differentiation, respectively. Each of the promoter sequences was cloned into a replication-deficient adenoviral vector containing the luciferase reporter gene. Previous studies showed that a human submandibular gland cell line (HSG) differentiated into acinar cells when cultured on a reconstituted basement membrane matrix (Matrigel). The luciferase activity of the amylase promoter vector (AdAMY-luc) was low in HSG cells cultured on plastic, where they grow as an epithelial monolayer. The promoter activity increased approximately tenfold when HSG cells were cultured on Matrigel and developed an acinar phenotype. Under the same conditions, the luciferase activity of the kallikrein promoter (AdKALL-luc) was not induced. Because HSG cells demonstrate acinar cell morphology, but not amylase gene expression, when cultured on laminin-1, certain soluble components of Matrigel were tested for their ability to induce the amylase promoter during in vitro differentiation of acinar cells. We find that epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-α), which are present in the basement membrane, and hepatocyte growth factor (HGF) increase activity of the amylase promoter. Other basement membrane-derived growth factors such as TGF-β, basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PGDF), as well as tumor necrosis factor (TNF-α), keratinocyte growth factor (KGH), nerve growth factor (NGF) and interferon gamma (IFN-γ) were inactive. This system will be further exploited to study the mechanisms by which extracellular matrix molecules and growth factors regulate salivary acinar cell differentiation. J Cell Physiol 177:628-635, 1998. Published 1998 Wiley-Liss, Inc.
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  • 12
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of HSP27 in cell growth and resistance to stress was investigated using murine fibrosarcoma L929 cells (normally devoid of constitutively expressed small HSPs) and human osteoblast-like SaOS-2 cells stably transfected with a human hsp27 expression vector. Our data showed that our L929 cells were more resistant to oxidative stress than generally observed for this line. Production of HSP27 in these cells led to a marked decrease in growth rate associated with a series of phenotypical changes, including cell spreading, cellular and nuclear hypertrophy, development of an irregular outline, and a tremendous accumulation of actin stress fibers. By contrast, none of these changes was observable in SaOS-2/hsp27 transfectants overexpressing the protein product. Together, these observations are consistent with a cause-to-effect cascade relationship between increased (or induced) HSP27 expression, changes in cytoskeletal organization, and decreased growth. On the other hand, whereas the transfection of the hsp27 gene increased the cell resistance to heat in both cell lines, only in SaOS-2 cells was this associated with protection to the cytotoxic action of tumor necrosis factor-alpha (TNF-α) and etoposide. Unexpectedly, L929/hsp27 transfectants exhibited an increased sensitivity to both agents and also to H2O2. These data thus imply that different mechanisms are involved in the cell resistance to heat shock and to the cytotoxic action of TNF-α, etoposide, and H2O2. They also plead against the simple view that overexpression of a phosphorylatable HSP27 would necessarily be beneficial in terms of increased cell resistance to any type of stress. Our data further indicate that the role of HSP27 in cellular resistance to stress and in cell proliferation involves different targets and that the ultimate result of its interference with these processes depends on the intracellular context in which the protein is expressed. J Cell Physiol 177:606-617, 1998. © 1998 Wiley-Liss, Inc.
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  • 13
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using an expression cloning approach, we identified and cloned a novel intracellular protein produced by osteoclasts that indirectly induces osteoclast formation and bone resorption, termed OSF. Conditioned media from 293 cells transiently transfected with the 0.9 kb OSF cDNA clone stimulated osteoclast-like cell formation in both human and murine marrow cultures in the presence or absence 10-9 M 1,25-dihydroxyvitamin D3. In addition, conditioned media from 293 cells transfected with the OSF cDNA clone enhanced the stimulatory effects of 1,25-(OH)2D3 on bone resorption in the fetal rat long bone assay. In situ hybridization studies using antisense oligomers showed expression of OSF mRNA in highly purified osteoclast-like cells from human giant cell tumors of the bone. Northern blot analysis demonstrated ubiquitous expression of a 1.3 kb mRNA that encodes OSF in multiple human tissues. Sequence analysis showed the OSF cDNA encoded a 28 kD peptide that contains a c-Src homology 3 domain (SH3) and ankyrin repeats, suggesting that it was not a secreted protein, but that it was potentially involved in cell signaling. Consistent with these data, immunoblot analysis using rabbit antisera against recombinant OSF demonstrated OSF expression in cell lysates but not in the culture media. Furthermore, recombinant OSF had a high affinity for c-Src, an important regulator of osteoclast activity. Taken together, these data suggest that OSF is a novel intracellular protein that indirectly enhances osteoclast formation and osteoclastic bone resorption through the cellular signal transduction cascade, possibly through its interactions with c-Src or other Src-related proteins. J Cell Physiol 177:636-645, 1998. © 1998 Wiley-Liss, Inc.
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  • 14
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The addition of dexamethasone (dex) to human fibroblast cultures has been found to elicit enhanced proliferation. This enhancement is manifested by an increase in the initial growth rate, saturation density, and proliferative life span of WI-38 fibroblast cultures grown in the presence of dex. We examined the acute effects of dex on a number of growth-related genes in WI-38 cells. Our results show a decrease in the level of the cyclin-dependent kinase inhibitor p21Waf1/Cip1/Sdi1 in response to dex. In addition, the level of the insulin-like growth factor type 1 receptor (IGF-1R) is increased in dex-treated cells. These changes are correlated with changes in the activity of the p21Waf1/Cip1/Sdi1 and IGF-1R promoters. The results presented in this report suggest that dex may delay growth arrest in response to contact inhibition, as well as during cellular senescence. Thus, dex may act at multiple levels to enhance cellular proliferation in WI-38 cells: first, to decrease the level of an inhibitor of cell-cycle progression, and second, to increase the sensitivity of WI-38 cells to the proliferative effects of IGF-1. These acute effects may cooperate with other, as yet uncharacterized effects, to result in the enhanced proliferation seen in the presence of dex. J. Cell. Physiol. 177:396-401, 1998. © 1998 Wiley-Liss, Inc.
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  • 15
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 402-410 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Potassium (K+) conductances are known to be involved in cell proliferation of a number of nonexcitable cell types. The nature of the mechanism by which K+ channel inhibition reduces cell proliferation has remained elusive despite intensive search. We investigated whether such a phenomenon could be demonstrated in excitable cells, using the GH3 pituitary cell line as a cell model. Our aims were: (1) to study the effect of K+ channel inhibition on the proliferation of GH3 cells; and (2) to investigate the putative intracellular signals involved in this inhibition. Tetraethylammonium chloride (TEA), a blocker of the calcium (Ca2+)-dependent K+ conductances of GH3, was found to reversibly inhibit cell proliferation, as measured by 3H-thymidine incorporation. Cell cycle block specifically occurred at the G1/S phase of the cell cycle. This inhibition of proliferation was observed for 1-4 mM TEA, which suppressed most of the Ca2+-activated K+ current and part of the inward rectifying K+ current, as shown by electrophysiological experiments. Increasing extracellular K+ concentrations with KCl also inhibited cell proliferation in a dose-dependent manner. Both TEA and KCl depolarized the cells and increased intracellular Ca2+ levels ([Ca2+]i), showing that, in this type of excitable cell, inhibition of cell proliferation can be associated with elevated Ca2+ levels. Ca2+ and membrane resting potential (MRP) were considered as possible messengers of this inhibition. Our results suggest that cell cycle arrest of GH3 cells by K+ channel block probably involves an additional pathway, distinct from those of Ca2+ and MRP. J. Cell. Physiol. 177:402-410, 1998. © 1998 Wiley-Liss, Inc.
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  • 16
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 387-395 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previously, we reported that unaggressive, growth factor-dependent FET human colon carcinoma cells downregulated their transforming growth factor alpha (TGFα) expression in a quiescent state (G0/G1) induced by growth factor and nutrient deprivation (Mulder, 1991, Cancer Res., 51:2256-2262). In contrast, highly aggressive, growth factor-independent HCT116 human colon carcinoma cells aberrantly upregulated this autocrine activity in the quiescent state (Mulder, 1991, Cancer Res., 51:2256-2262; Howell et al., 1998, Mol. Cell. Biol., 18:303-313). In this report, the role of autocrine TGFα and the mechanism of its regulation of expression during reentry into the cell cycle from a noncycling growth state were determined in FET cells. Optimal induction of DNA synthesis from a quiescent state in FET cells is dependent upon autocrine TGFα as well as exogenous transferrin and insulin. Reentry into the cell cycle resulting from treatment with exogenous transferrin and insulin resulted in ∼3-fold induction of TGFα expression within 1 hr. TGFα induction was controlled at the transcription level, and the cis-controlling element was localized to the region between bp -370--201 relative to the translation start codon within the TGFα promoter. Thus neutralization of autocrine TGFα protein revealed that the induced TGFα autocrine activity was necessary for DNA synthesis and acted only in the early G1 phase of the cell cycle. Blockade of autocrine TGFα expression early in the cell cycle resulted in the reduction of DNA synthesis, whereas treatment with neutralization antibody at later times had no effect. This suggested that autocrine TGFα functions to initiate cell growth from noncycling states. This was further confirmed by the dependence of FET cells upon autocrine TGFα for colony formation in experiments where the plating density was sufficiently low to generate a lag phase in tissue culture. In contrast, TGFα autocrine activity was not required for exponential phase cells, as evidenced by the failure of TGFα neutralizing antibody to inhibit proliferation in this growth state. Taken together, these results suggest that autocrine TGFα acts primarily in the process of growth initiation by moving cells from a noncycling state back into the cell cycle, rather than supporting cell growth already initiated. J. Cell. Physiol. 177:387-395, 1998. © 1998 Wiley-Liss, Inc.
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  • 17
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Basic fibroblast growth factor (bFGF, FGF-2) is progressively lost from mammary epithelial cells as they become malignant. To investigate the effects of restoring the expression of bFGF in breast cancer cells, we constructed MCF-7 cells that permanently overexpress 18-kD cytoplasm-localizing bFGF (MCF-7/ΔAFGF(18) cells) and cells that express both the 18-kD along with the 22- and 24-kD nucleus-localizing bFGF peptides (MCF-7/NCFFGF(18,22,24) cells), using retroviral transduction. These stable cell constructs grew more slowly and had a larger fraction of their populations in the G0/G1 phase of the cell cycle than control cells. All forms of bFGF were eluted from MCF-7/NCFFGF(18,22,24) cell monolayers with 2 M NaCl, in contrast to fibroblasts that were demonstrated to secrete only the 18-kD bFGF isoform. High-affinity binding of 18-kD 125I-bFGF to these cells was significantly decreased, probably because of competitive binding by the autocrine-secreted bFGF. Recombinant 18-kD bFGF that was previously demonstrated in our laboratory to inhibit proliferation, activate MAP kinase, and induce the cyclin-dependent kinase inhibitor p21WAF1/CIP1 in MCF-7 cells, further inhibited MCF-7/ΔAFGF(18) cells but had no effect on MCF-7/NCFFGF(18,22,24) cells. The total cellular content of the high-affinity FGF receptors 1-3 was unchanged, but FGF receptor 4 was decreased in MCF-7/NCFFGF(18,22,24) cells. Both cell types overexpressing bFGF isoforms had elevated levels of the cyclin-dependent kinase inhibitor p27Kip1 but not that of p21WAF1/CIP1. In MCF-7/ΔAFGF(18) cells, FGFR1 and MAP kinase were constitutively phosphorylated. Exogenous recombinant 18-kD bFGF did not accentuate these effects but did induce an increase in the levels of p21WAF1/CIP1 corresponding to the further inhibition induced by exogenous bFGF in these cells. In MCF-7/NCFFGF(18,22,24) cells, FGFR1 and MAP kinase were not phosphorylated at baseline nor upon stimulation with recombinant bFGF, and exogenous bFGF only had a minimal effect on low steady-state p21WAF1/CIP1 levels. However, stimulation of these cells with phorbol ester or insulin did result in MAP kinase phosphorylation. While growth-inhibited in the G1 phase of the cell cycle, MCF-7/NCFFGF(18,22,24) cells retained active isoforms of cdk2 and the hyperphosphorylated form of Rb. These data suggest that high molecular weight forms of bFGF overexpressed in MCF-7 cells do not activate the receptor-mediated MAP kinase pathway, and do not induce p21WAF1/CIP1 in an autocrine manner, but inhibit proliferation through other, possibly direct nuclear signalling mechanisms. J. Cell. Physiol. 177:411-425, 1998. © 1998 Wiley-Liss, Inc.
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  • 18
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bone marrow stromal cells (BMSCs) are a heterogeneous population of cells derived from colony-forming units-fibroblastic (CFU-Fs). These cells reside in the bone marrow cavity and are capable of differentiating into several cell phenotypes including osteoblasts, chondroblasts, hematopoiesis-supporting stromal cells, and adipocytes. However, the factors that regulate the proliferation and differentiation of the BMSC population are for the most part unknown. Since many members of the receptor tyrosine kinase (RTK) family have been shown to participate in growth control of various mesenchymal cell populations, in this study we examined the expression and function of RTKs in the BMSC population. Degenerate oligonucleotides corresponding to two conserved catalytic domains of the RTK family and RT-PCR were used initially to determine which RTKs are expressed in the human BMSC (hBMSC) system. After subcloning the amplification product generated from mRNA of a multicolony-derived hBMSC strain, PDGF receptor (β), EGF receptor, FGF receptor 1, and Axl were identified by DNA sequencing of 26 bacterial colonies. Furthermore, PDGF and EGF were found to enhance BMSC growth in a dose-dependent manner and to induce tyrosine phosphorylation of intracellular molecules, including the PDGF and EGF receptors themselves, demonstrating the functionality of these receptors. On the other hand, bFGF was found to have little effect on proliferation or tyrosine phosphorylation. Since single colony-derived hBMSC strains are known to vary from one colony to another in colony habit (growth rate and colony structure) and the ability to form bone in vivo, the expression levels of these RTKs were determined in 18 hBMSC clonal strains by semiquantitative RT-PCR and were found to vary from one clonal strain to another. While not absolutely predictive of the osteogenic capacity of individual clonal strains, on average, relatively high levels of PDGF-receptor were found in bone-forming strains, while on average, nonbone-forming strains had relatively high levels of EGF-receptor. Taken together, these results indicate that RTKs play a role in the control of hBMSC proliferation, and that the differential pattern of RTK expression may be useful in correlating the biochemical properties of individual clonal strains with their ability to produce bone in vivo. J. Cell. Physiol. 177:426-438, 1998. © 1998 Wiley-Liss, Inc.
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  • 19
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Vascular endothelial growth factor-C (VEGF-C) is a recently characterized member of the VEGF family of angiogenic polypeptides. We demonstrate here that VEGF-C is angiogenic in vitro when added to bovine aortic or lymphatic endothelial (BAE and BLE) cells but has little or no effect on bovine microvascular endothelial (BME) cells. As reported previously for VEGF, VEGF-C and basic fibroblast growth factor (bFGF) induced a synergistic in vitro angiogenic response in all three cells lines. Unexpectedly, VEGF and VEGF-C also synergized in the in vitro angiogenic response when assessed on BAE cells. Characterization of VEGF receptor (VEGFR) expression revealed that BME, BAE, and BLE cell lines express VEGFR-1 and -2, whereas of the three cell lines assessed, only BAE cells express VEGFR-3. We also demonstrate that VEGF-C increases plasminogen activator (PA) activity in the three bovine endothelial cell lines and that this is accompanied by a concomitant increase in PA inhibitor-1. Addition of α2-antiplasmin to BME cells co-treated with bFGF and VEGF-C partially inhibited collagen gel invasion. These results demonstrate, first, that by acting in concert with bFGF or VEGF, VEGF-C has a potent synergistic effect on the induction of angiogenesis in vitro and, second, that like VEGF and bFGF, VEGF-C is capable of altering endothelial cell extracellular proteolytic activity. These observations also highlight the notion of context, i.e., that the activity of an angiogenesis-regulating cytokine depends on the presence and concentration of other cytokines in the pericellular environment of the responding endothelial cell. J. Cell. Physiol. 177:439-452, 1998. © 1998 Wiley-Liss, Inc.
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  • 20
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell cycle control of histone H4 gene transcription is mediated by the multipartite promoter domain H4-Site II, which supports transcriptional activation at the G1/S phase transition and modulates basal H4 gene transcription. Proliferation-specific transcription is determined by the integrated activities of three distinct promoter factors interacting with H4-Site II: the interferon regulatory factor IRF-2 (synonymous with HiNF-M), HiNF-D (a complex between the homeodomain protein CDP-cut and the cell cycle mediators CDC2, cyclin A and pRB), as well as HiNF-P/H4TF-2. However, the contribution of HiNF-D to the enhancement and/or suppression of H4 gene transcription at specific cell cycle stages remains to be established. We used a panel of synchronized HeLa S3 cell lines containing stably integrated H4 promoter/CAT reporter gene constructs with mutations in H4-Site II. The temporal regulation of CAT mRNA accumulation under the control of the H4 promoter was analyzed by RNase protection analysis. Our main finding is that mutation of the HiNF-D/CDP-cut binding site alters the timing of histone gene activation during the cell cycle. Furthermore, our data indicate that HiNF-P/H4TF-2 may functionally compensate for HiNF-M/IRF-2 at Site II to regulate histone H4 gene transcription in HeLa S3 cervical carcinoma cells during early S phase. We postulate that HiNF-D (CDP-cut/cyclin A/CDC2/pRB containing complex) promotes HiNF-M/IRF-2 (and/or HiNF-P/H4TF-2) dependent histone H4 gene activation at the G1/S phase transition and attenuates H4 gene transcription at later cell cycle stages. The mechanistic division in the gene regulatory functions of the three H4-Site II binding proteins may ensure that histone H4 gene expression is stringently coupled with the onset of S phase in response to growth factor/cytokine-induced cell cycle progression. J. Cell. Physiol. 177:453-464, 1998. © 1998 Wiley-Liss, Inc.
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  • 21
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    Journal of Cellular Physiology 177 (1998), S. 465-473 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human dermal fibroblasts suspended in a collagen matrix exhibit a 4-day delay in cell division, while the same cells in monolayer divided by day 1. The initial rates of 3H-thymidine incorporation by cells in monolayer or suspended in collagen were not significantly different. When suspended in collagen, there was a threefold increase in the proportion of cells in a tetraploidal (4N) DNA state compared to the same cells in monolayer. Flow cytometry analysis and 3H-thymidine incorporation studies identified the delay of cell division as a consequence of a block in the G2/M of the cell cycle and not an inhibition of DNA synthesis. The inclusion of 150 μ/ml of hyaluronic acid (HA) in the manufacture of fibroblast populated collagen lattices (FPCL) caused a stimulation of cell division, as determined by cell counting; increased the expression of tubulin, as determined by Western blot analysis; and reduced the proportion of cells in a 4N state, as determined by flow cytometry. HA added to the same cells growing in monolayer produced a minimal increase in the rate of cell division or DNA synthesis. HA supplementation of FPCLs stimulated cell division as well as tubulin concentrations, but it did not enhance lattice contraction. The introduction of tubulin isolated from pig brain or purchased tubulin into fibroblasts by electroporation prior to their transfer into collagen lattices promoted cell division in the first 24 hours and enhanced FPCL contraction. It is proposed that tubulin protein, the building blocks of microtubules, is limited in human fibroblasts residing within a collagen matrix. When human fibroblasts are suspended in collagen, one effect of added HA may be to stimulate the synthesis of tubulin which assists cells through the cell cycle. J. Cell. Physiol. 177:465-473, 1998. © 1998 Wiley-Liss, Inc.
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  • 22
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    Journal of Cellular Physiology 177 (1998), S. 474-482 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study we examined the regulation of cdk1 expression in normal human epidermal keratinocytes (HEKs) and neoplastic keratinocytes. Keratinocytes were growth-arrested by allowing the cells to grow to confluence or by treating them with interferon-gamma (IFNγ) or 12-O-tetradecanoyl phorbol-13-acetate (TPA). RT-PCR and Western blot analysis demonstrated that cdk1 was profoundly reduced in growth-arrested HEKs when compared with dividing HEKs. In contrast, a squamous carcinoma cell line, SCC25, did not growth-arrest in response to growth inhibitors and did not downregulate cdk1 expression. Transfection of HEKs with a reporter gene driven off a 2.5-kb fragment of the human cdk1 promoter indicated that the downregulation of cdk1 upon growth arrest was transcriptional. Deletion mapping of the cdk1 promoter indicated that a repressor region was located between -949--722 bp. This repressor region was not operative in the SCC25 cells. Examination of DNA:protein binding complexes by gel-shift analysis indicated that nuclear factors from both proliferative and growth-arrested cells bound to the DNA fragment spanning -949--722 bp. Further analysis revealed that this binding could be resolved into a constitutive and growth arrest-specific complex that bound in a similar fashion to regions spanning -892--831 bp and -831--774 bp, respectively. The putative growth arrest-specific complex was not found in contact-inhibited fibroblasts and was found at very low levels in SCC25 cells, indicating that the putative repressor binding was growth arrest-specific and possibly keratinocyte-specific. The binding complexes bound to these two fragments were localized, by competition analysis, to regions -874--853 bp and -830--800 bp. This is the first report of a transcriptional repressor being operative during keratinocyte growth arrest. J. Cell. Physiol. 177:474-482, 1998. © 1998 Wiley-Liss, Inc.
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  • 23
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    Journal of Cellular Physiology 177 (1998), S. 483-492 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Treatment with the sulfhydryl oxidant diamide denatures and aggregates cellular proteins, which prior studies have implicated as an oxidative damage that activates the heat shock transcription factor and induces thermotolerance. This study was initiated to further characterize cellular response to diamide-denatured proteins, including their involvement in diamide cytotoxicity. Cytotoxic diamide exposures at 37.0°C denatured and aggregated cellular proteins in a manner that was proportional to cell killing, but this correlation was different than that established for heated cells. Diamide exposures at 24.0°C were orders of magnitude less cytotoxic, with little additional killing occurring after diamide was removed and cells were returned to 37.0°C. Thus, protein denaturation that occurred at 37.0°C, after proteins were chemically destabilized by diamide at 24.0°C [Freeman et al., J. Cell. Physiol., 164:356-366 (1995) Senisterra et al., Biochemistry 36: 11002-11011 (1997)], had little effect on cell killing. Thermotolerance protected cells against diamide cytotoxicity but did not reduce the amount of denatured and aggregated protein observed immediately following diamide exposure. However, denatured/aggregated proteins in thermotolerant cells were disaggregated within 17 h following diamide exposure, while no disaggregation was observed in nontolerant cells. This more rapid disaggregation of proteins may be one mechanism by which thermotolerance protects cells against diamide toxicity, as it has been postulated to do against heat killing. As with heat shock, nontoxic diamide exposures induced maximal tolerance against heat killing; however, there was no detectable, increased synthesis of heat shock proteins. Thus, diamide treatment proved to be a reproducible procedure for inducing a phase of thermotolerance that does not require new heat shock protein (HSP) synthesis, without having to use transcription or translation inhibitors to suppress HSP gene expression.These results complement those from studies with other stresses to establish the importance of protein denaturation/aggregation as a cytotoxic consequence of stress and a trigger for thermotolerance induction. The data also illustrate that differences in how proteins are denatured and aggregated can affect their cytotoxicity and the manner in which thermotolerance is expressed. J. Cell. Physiol. 177:483-492, 1998. © 1998 Wiley-Liss, Inc.
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  • 24
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    Journal of Cellular Physiology 177 (1998), S. 499-499 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: No abstract.
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  • 25
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    Journal of Cellular Physiology 177 (1998), S. 501-506 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: CDK9 is a cdc2-related kinase protein. Previously named PITALRE, this protein is a serine-threonine kinase involved in many physiological processes. Unlike most of the cdc2-like kinases, its activity is not cell cycle-regulated. CDK9 acts preferentially in processes different from cell-cycle regulation, such as differentiation. Its cyclin partners, cyclins of T family, recently have been isolated. CDK9 immunoprecipitates with several unidentified polypeptides that may regulate its kinase activity. CDK9 has been shown to associate with the HIV-Tat protein, suggesting a possible involvement in AIDS. CDK9 recently was shown to be responsible for the kinase activity associated with the TAK complex and with the P-TEFb complex, suggesting activity also in the transcription process. J Cell Physiol 177:501-506, 1998. © 1998 Wiley-Liss, Inc.
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  • 26
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    Journal of Cellular Physiology 177 (1998), S. 493-498 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ultraviolet light A (UVA) is shown to play an augmentative or synergistic role with UVB in pathophysiological conditions induced by solar radiation. Thus, UVA would contribute significantly to the development of skin malignancies. It remains unclear, however, how UVA contributes to solar radiation-induced immune suppression. Keratinocytes (KC) produce cytokines which are a significant mediator of inflammatory and immunologic reactions in skin exposed to solar radiation and are a potent mediator in the induction of immune suppression. To examine if UVA alters the expression and production of cytokines from KC, normal human keratinocytes (HuSK) were cultured and exposed to UVA at doses ranging between 2.5 and 20 kJ/m2. Constitutive expression of the p35 subunit of interleukin (IL)-12 was detected by reverse transcription-polymerase chain reaction (RT-PCR) and the p40 subunit was induced by UVA irradiation dose dependently. IL-12 protein was also detected in the supernatants from UVA-irradiated HuSK by enzyme-linked imuunosorbent assay (ELISA) and confirmed by a bioassay. On the other hand, the same doses of UVA did not induce IL-10 mRNA or IL-10 protein which has been shown to be one of the cytokines responsible for the induction of UVB-induced immunosuppression. Considering that IL-12 promotes activation of Th1 cells and prevents the activation of Th2 cells and that administration of IL-12 has been shown to block the induction of immune suppression in UV-irradiated animals, our results suggest that UVA modulates skin immune function distinctively from UVB by affecting the balance between IL-10 and IL-12 produced from KC. J. Cell. Physiol. 177:493-498, 1998. © 1998 Wiley-Liss, Inc.
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  • 27
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    Journal of Cellular Physiology 177 (1998), S. 507-517 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Neuropeptides, including mammalian bombesin-like peptides, act as potent cellular growth factors and have been implicated in a variety of normal and abnormal processes, including development, inflammation, and malignant transformation. These signaling peptides exert their characteristic effects on cellular processes by binding to specific G protein-coupled receptors (GPCR) on the surface of their target cells. Typically, the binding of a neuropeptide to its cognate GPCR triggers the activation of multiple signal transduction pathways that act in a synergistic and combinatorial fashion to relay the mitogenic signal to the nucleus and promote cell proliferation. A rapid increase in the synthesis of lipid-derived second messengers with subsequent activation of protein phosphorylation cascades is an important early response to neuropeptides. An emerging theme in signal transduction is that these agonists also induce rapid and coordinate tyrosine phosphorylation of cellular proteins including the nonreceptor tyrosine kinase p125fak and the adaptor proteins p130cas and paxillin. This tyrosine phosphorylation pathway depends on the integrity of the actin cytoskeleton and requires functional Rho. The purpose of this article is to review recent advances in unraveling the pathways that play a role in transducing mitogenic and migratory responses induced by G protein-coupled neuropeptide receptor agonists. J Cell Physiol 177:507-517, 1998. © 1998 Wiley-Liss, Inc.
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  • 28
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The pentameric B subunit of verotoxin (VT) mediates the attachment to cell surface globotriaosyl ceramide (Gb3) to facilitate receptor-mediated endocytosis of the toxin. In highly toxin-sensitive tumor cells, the holotoxin and VT1 B subunit is targeted intracellularly to elements of the endoplasmic reticulum (ER)/nuclear membrane. In less sensitive cells, the toxin is targeted to components of the Golgi apparatus. We have studied two cell systems: the induced VT hypersensitivity of human astrocytoma cell lines cultured in the presence of sodium butyrate (compared to sodium propionate and capronate) and the increased VT sensitivity of multiple drug-resistant mutants as compared to parental human ovarian carcinoma cells. In both cases, a difference in the intracellular retrograde transport of the receptor-bound internalized toxin to the ER/nuclear envelope, as opposed to the Golgi, correlated with a 〉1,000-fold increase in cell sensitivity to VT. This change in intracellular routing may be due to sorting of Gb3 fatty acid isoforms, since nuclear targeting was found in turn to correlate with the preferential synthesis of Gb3 containing shorter chain (primarily C16) fatty acid species. We propose that the isoform-dependent traffic of Gb3 from the cell surface to the ER/nuclear membrane provides a new signal transduction pathway for Gb3 binding proteins. J Cell Physiol 177:646-660, 1998. © 1998 Wiley-Liss, Inc.
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  • 29
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 57-78 
    ISSN: 0271-2091
    Keywords: parallel processing ; domain partitioning ; hybrid grids ; grid adaptation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A parallel finite volume method for the Navier-Stokes equations with adaptive hybrid prismatic/tetrahedral grids is presented and evaluated in terms of parallel performance. A new method of domain partitioning for complex 3D hybrid meshes is also presented. It is based on orthogonal bisection of a special octree corresponding to the hybrid mesh. The octree is generated automatically and can handle any type of 3D geometry and domain connectivity. One important property of the octree-based partitioning that is exploited is the octree's ability to yield load-balanced partitions that follow the shape of the geometry. This biasing of the octree results in a reduced number of grid elements on the interpartition boundaries and thus fewer data to communicate among processors. Furthermore, the octree-based partitioning gives similar quality of partitions for very different geometries, while requiring minimal user interaction and little computational time. The partitioning method is evaluated in terms of quality of the subdomains as well as execution time. Viscous flow simulations for different geometries are employed to examine the effectiveness of the octree-based partitioning and to test the scalability of parallel execution of the Navier-Stokes solver and hybrid grid adapter on two different parallel systems, the Intel Paragon and the IBM SP2. © 1998 John Wiley & Sons, Ltd.
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  • 30
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 79-100 
    ISSN: 0271-2091
    Keywords: volume-of-fluid method ; free surface flows ; second-order model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: To improve the numerical analysis of free surface convection and interface reconstruction, both first- and second-order algorithms are developed based on the volume-of-fluid method. The methodology applied to the second-order model is to define the second-order linear curve having both face slopes as near horizontal as possible while satisfying the cell's defined volume fraction.The second-order method is compared with the FLAIR method and the first-order method through simulation of the convection for various sizes of circular liquid shapes and solitary waves. For small curvature of the free surface, e.g. circles with large diameter, linear methods such as the FLAIR method and the first-order method show relatively good predictions. However, for large-curvature configurations, e.g. circles with relatively small diameter or solitary waves, the linear approach shows large distortion of the free surface. In contrast, the second-order model always shows powerful prediction capabilities of free surface convection. © 1998 John Wiley & Sons, Ltd.
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  • 31
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 101-121 
    ISSN: 0271-2091
    Keywords: Riemann solvers ; Eulerian schemes ; detonations ; shock tracking ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper compares several high-resolution schemes for the computation of detonation waves in solid explosives. The essential difficulty in comparison with the usual application domain of these schemes is due to the complexity and variety of the equations of state which are used. The HLLC Riemann solver is used in the context of an Eulerian MUSCL scheme and in conjunction with a shock-tracking scheme. The motivation and justification for the various choices in the building of these schemes are discussed. The accuracy of both schemes, full Eulerian and shock-tracking variant, is clearly demonstrated. In addition, the validity of the results is shown. For one-dimensional applications the shock-tracking scheme is very accurate and relatively simple. For multidimensional applications it is recommended that the full Eulerian version be used. © 1998 John Wiley & Sons, Ltd.
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  • 32
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 177-197 
    ISSN: 0271-2091
    Keywords: unsteady flow ; lifting-line ; numerical computation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents the basis of a computational time-marching approach, for large-aspect ratio lifting systems submitted to unsteady motions, using the lifting-line concept. When engineering requires such an approach, quasi-steady ones are currently encountered, which are based on Prandtl's lifting-line approach for steady flows. The results of recent theoretical works on the unsteady lifting-line, based on the matched asymptotic expansion technique, allow one to improve, on sound theoretical foundations, this quasi-steady approach. The proposed approach solves a first-order approximation of the unsteady outer problem for the time-evolution of the spanwise circulation distribution along the lifting-line. It introduces, in the same kind of process as Prandtl's one, for each span section, an unsteady two-dimensional description of the aerofoil behaviour together with a formulation for the three-dimensional unsteady induced velocity on the lifting-line. The approach's validity is examined through a simple numerical implementation for three wing motion cases. Considering the numerical results it produces, it can be stated that the unsteady lifting-line model implementation can be considered as time-consistent, whereas the quasi-steady one cannot. Furthermore, the approach presented here allows large time steps, even for very unsteady wing motions, and compares favourably with some classical results of R. T. Jones. © 1998 John Wiley & Sons, Ltd.
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  • 33
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 217-247 
    ISSN: 0271-2091
    Keywords: puffs and thermals ; turbulence modelling ; jets and plumes ; environmental fluid mechanics ; vortex flow ; added mass ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The time evolution of a line puff, a turbulent non-buoyant element with significant momentum, is studied using the renormalization group (RNG) k-∊ model. The numerical results show that the puff motion is characterized by a vortex pair flow; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless time of around 30. The added mass coefficient of the puff motion is found to be approximately unity. The predicted puff flow and mixing rate are substantially similar to those obtained from the standard k-∊ model and are well supported by experimental data. The computed scalar field reveals significant secondary concentration peaks trailing behind in the wake of the puff. The present results suggest that the overall mixing rate of a puff is primarily determined by the large-scale motion and that streamline curvature probably plays a minor role. © 1998 John Wiley & Sons, Ltd.
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  • 34
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 251-280 
    ISSN: 0271-2091
    Keywords: turbulence modelling ; eddy viscosity ; second-moment closure ; tidal flows ; finite volume ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper employs one-point, linear eddy viscosity and differential second-moment (DSM) turbulence closures to predict the turbulent characteristics of both rectilinear and circular tidal flows. The numerical scheme is based on a finite volume approach applied to a non-staggered grid such that all flow variables are stored at one and the same set of nodes. Numerical stability is maintained through the implementation of apparent viscosities and source term linearization, which are essential if eddy viscosity terms are absent. A stable algorithm is devised for the Reynolds stresses which includes a non-linear velocity smoothing in order to stabilise the numerical scheme during flow reversal and relaminarization. Favourable agreement with the experimental rectilinear tidal data of Schröder (Tech. Rep. GK55 87/E/16, GKSS-Forshungszentrum Geesthacht, 1983) and McClean (Turbulence and Sediment Transport Measurements in a North Sea Tidal Inlet (the Jade), Springer, New York, 1987, p. 436) is reported. Numerical calculations of circular tidal flows are also presented which were motivated by the preliminary investigations of Davies and Jones (Int. j. numer. meth. fluids,12, 17 (1991)) and Davies (Continental Shelf. Res., 11, 1313 (1991)), who employed the one-equation, k-l, eddy viscosity turbulence model to simulate rectilinear and circular tidal flows. © 1998 John Wiley & Sons, Ltd.
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  • 35
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 323-343 
    ISSN: 0271-2091
    Keywords: mixed convection ; finite volume algorithm ; eccentricity ; Nusselt number ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A computational study is performed on two-dimensional mixed convection in an annulus between a horizontal outer cylinder and a heated, rotating, eccentric inner cylinder. The computation has been done using a non-orthogonal grid and a fully collocated finite volume procedure. Solutions are iterated to convergence through a pressure correction scheme and the convection is treated by Van Leer's MUSCL scheme. The numerical procedure adopted here can easily eliminate the ‘Numerical leakage’ phenomenon of the mixed convection problem whereby strong buoyancy and centrifugal effects are encountered in the case of a highly eccentric annulus. Numerical results have been obtained for Rayleigh number Ra ranging from 7×103 to 107, Reynolds number Re from 0 to 1200 and Prandtl number Pr from 0.01 to 7. The mixed rotation parameter σ (=Ra/PrRe2) varies from ∞ (pure natural convection) to 0.01 with various eccentricities ε. The computational results are in good agreement with previous works which show that the mixed convection heat transfer characteristics in the annulus are significantly affected by σ and ε. The results indicate that the mean Nusselt number Nu increases with increasing Ra or Pr but decreases with increasing Re. In the case of a highly eccentric annulus the conduction effect becomes predominant in the throat gap. Hence the crucial phenomenon on whereby Nu first decreases and then increases can be found with increasing eccentricity. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 303-322 
    ISSN: 0271-2091
    Keywords: hierarchical grids ; quadtrees ; adaptive remeshing ; separated flows ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper describes the use of adaptive hierarchical grids to predict incompressible separated flow at low Reynolds number. The grids consist of a quadtree system of hierarchical Cartesian meshes which are generated by recursive subdivision about seeding points. The governing equations are discretized in collocated primitive variable form using finite volumes and solved using a pressure correction scheme. The mesh is locally adapted at each time step, with panel division or removal dependent on the vorticity magnitude. The resulting grids have fine local resolution and are economical in array size. Results are presented for unidirectional, impulsively started flow past a circular and a square cylinder at various Reynolds numbers up to 5000 and 250 respectively. It is clear that hierarchical meshes may offer gains in efficiency when applied to complex flow domains or strongly sheared flows. However, as expected, the stepped approximation to curved boundaries resulting from the Cartesian quadtree representation adversely affects the accuracy of the results for flow past a circular cylinder. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 443-457 
    ISSN: 0271-2091
    Keywords: direct numerical simulation ; 2D temporal disturbance ; plane Poiseuille flow ; finite difference method ; transient non-linear equation ; stream-function-vorticity equation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A direct numerical scheme is developed to study the temporal amplification of a 2D disturbance in plane Poiseuille flow. The transient non-linear Navier-Stokes equations are applied in a region of wavelength moving with the wave propagation speed. The complex amplitude involved in the perturbation functions is considered as the initial input of the non-linear stability equations. In this study a fully implicit finite difference scheme with five points in the flow direction and three points in the normal direction is developed so that numerical simulation of the amplification of a two-dimensional temporal disturbance in plane Poiseuille flow can be investigated. The growth and decay of the disturbance with time are presented and neutral stability curves which are in good agreement with existing solutions can be determined. The critical conditions as a function of the amplitude A0 of the disturbance are presented. Fixing the wavelength, the Navier-Stokes equations are solved up to Re=10,000 a friction factor increasing with Reynolds number is observed. The 2D non-linear behaviour of the streamfunction, vorticity and velocity components at Re=10,000 are also exhibited. © 1998 John Wiley & Sons, Ltd.
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  • 38
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 485-495 
    ISSN: 0271-2091
    Keywords: capillarity ; free surface ; finite elements ; validation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The mathematical formulation of the dynamics of free liquid surfaces including the effects of surface tension is governed by a non-linear system of elliptic differential equations. The major difficulty of getting unique closed solutions only in trivial cases is overcome by numerical methods. This paper considers transient simulations of liquid-gas menisci in vertical capillary tubes and gaps in the presence of gravity. Therefore the CFD code FIDAP 7.52 based on the Galerkin finite element method (FEM) is used. Calculations using the free surface model are presented for a variety of contact angles and cross-sections with experimental and theoretical verification. The liquid column oscillations are compared for numerical accuracy with a mechanical mathematical model, and the sensitivity with respect to the node density is investigated. The efficiency of the numerical treatment of geometric non-trivial problems is demonstrated by a prismatic capillary. Present restrictions limiting efficient transient simulations with irregularly shaped calculational domains are stated. © 1998 John Wiley & Sons, Ltd.
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  • 39
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 533-556 
    ISSN: 0271-2091
    Keywords: mixed finite elements ; finite volumes ; groundwater flow and transport ; biodegradation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical model for the simulation of flow and transport of organic compounds undergoing bacterial oxygen- and nitrate-based respiration is presented. General assumptions regarding microbial population, bacteria metabolism and effects of oxygen, nitrogen and nutrient concentration on organic substrate rate of consumption are briefly described. The numerical solution techniques for solving both the flow and the transport are presented. The saturated flow equation is discretized using a high-order mixed finite element scheme, which provides a highly accurate estimation of the velocity field. The transport equation for a sorbing porous medium is approximated using a finite volume scheme enclosing an upwind TVD shock-capturing technique for capturing concentration-unsteady steep fronts. The performance and capabilities of the present approach in a bio-remediation context are assessed by considering a set of test problems. The reliability of the numerical results concerning solution accuracy and the computational efficiency in terms of cost and memory requirements are also estimated. © 1998 John Wiley & Sons, Ltd.
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  • 40
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 501-517 
    ISSN: 0271-2091
    Keywords: Multiphase ; turbulent ; finite volumes ; structured grids ; compressible flows ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerically fast algorithm has been developed to solve the viscous two-phase flow in an axisymmetric rocket nozzle. A Eulerian-Eulerian approach is employed in the computation to couple the gas-particle flow. Turbulence closure is achieved using a Baldwin-Lomax model. The numerical procedure employs a multistage time-stepping Runge-Kutta scheme in conjunction with a finite volume method and is made computationally fast for the axisymmetric nozzle. The present numerical scheme is applied to compute the flow field inside JPL and AGARD nozzles. © 1998 John Wiley & Sons, Ltd.
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  • 41
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 627-635 
    ISSN: 0271-2091
    Keywords: arbitrary-order boundary element method ; non-singular formulation ; potential problems ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents a general direct integral formulation for potential flows. The singularities of Green's functions are desingularized theoretically, using a subtracting and adding back technique, so that Gaussian quadrature or any other numerical integration methods can be applied directly to evaluate all the integrals without any difficulty. When high-order quadrature formulas are applied globally, the number of unknowns can be reduced. Interpolation functions are not necessary for unknown variables in the present paper. Therefore, the present method is much simpler and more efficient than the conventional one. Several numerical examples are calculated and compared satisfactorily with analytical solutions or published results. © 1998 John Wiley & Sons, Ltd.
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  • 42
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 637-655 
    ISSN: 0271-2091
    Keywords: liquid flow ; energy transport ; electron-beam ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical analysis is made of the liquid flow and energy transport in a system to evaporate metals. The energy from an electron-beam heats an axisymmetric metal disk supported by a water-cooled platform. Metal evaporates from the surface of a hot pool of liquid which is surrounded by a shell of its own solid. Flow in the pool is strongly driven by temperature-induced buoyancy and capillary forces, and is located in the transition region between laminar and turbulent flow. The evaporation rate is strongly influenced by the locations of the free boundaries. A modified finite element method is used to calculate the steady state flow and temperature fields coupled with the interface locations. The mesh is structured with spines that stretch and pivot as the interfaces move. The discretized equations are arranged in an ‘arrow’ matrix and are solved using the Newton-Raphson method. The electron-beam power and platform contact resistance are varied for cases involving the evaporation of aluminum. The results reveal the interaction of liquid flow, heat transfer and free interfaces. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 697-712 
    ISSN: 0271-2091
    Keywords: viscoelastic ; boundary conditions ; tube tooling ; cable-coating ; finite elements ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A viscoelastic analysis is presented for model tube tooling, draw-down and combined geometry flows encountered in the cable coating industries. The work investigates the development of stress fields and studies the effect of varying entry flow stress boundary conditions. The analysis takes into account tube tooling and draw-down flow sections individually, and in combination. The flow behaviour of cable-coating grade low density polyethylene is studied assuming a viscoelastic, isothermal flow, and employing a Taylor-Petrov-Galerkin finite element scheme with an exponential Phan-Thien-Tanner constitutive model. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 725-747 
    ISSN: 0271-2091
    Keywords: unsteady two-body interaction ; potential flow theory ; boundary-integral method ; Lagrange's equation of motion ; generalized Taylor's formula ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: On the basis of the potential flow theory, Lagrange's equation of motion is used to study the unsteady ground-effect problem. The forces and moments acting on the moving body are solved in terms of the derivatives of added masses in which the generalized Taylor's formulae are applied. The singular integral equations used to solve the surface source intensities and their derivatives are regularized by the Gauss flux theorem and are therefore amenable to the direct use of the Gaussian quadrature formula. In illustration, the condition of a prolate spheroid moving in the fore-and-aft direction at constant speed past a flat ground with a protrusion is considered. The hydrodynamic forces and moments acting on the moving spheroid are investigated systematically by varying the size of the protrusion and the cruising height of the spheroid. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 791-809 
    ISSN: 0271-2091
    Keywords: open channel ; subcritical and supercritical flows ; TVD schemes ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Saint Venant equations for modelling flow in open channels are solved in this paper, using a variety of total variation diminishing (TVD) schemes. The performance of second- and third-order-accurate TVD schemes is investigated for the computation of free-surface flows, in predicting dam-breaks and extreme flow conditions created by the river bed topography. Convergence of the schemes is quantified by comparing error norms between subsequent iterations. Automatically calculated time steps and entropy corrections allow high CFL numbers and smooth transition between different conditions. In order to compare different approaches with TVD schemes, the most accurate of each type was chosen. All four schemes chosen proved acceptably accurate. However, there are important differences between the schemes in the occurrence of clipping, overshooting and oscillating behaviour and in the highest CFL numbers allowed by a scheme. These variations in behaviour stem from the different orders and inherent properties of the four schemes. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 771-789 
    ISSN: 0271-2091
    Keywords: three-dimensional numerical method ; hybrid method ; splitting method ; Eulerian-Lagrangian method ; shallow water equations ; sigma co-ordinate transformation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new efficient numerical method for three-dimensional hydrodynamic computations is presented and discussed in this paper. The method is based on the operator splitting method and combined with Eulerian-Lagrangian method, finite element method and finite difference method. To increase the efficiency and stability of the numerical solutions, the operator splitting method is employed to partition the momentum equations into three parts, according to physical phenomena. A time step is divided into three time substeps. In the first substep, advection and Coriolis force are solved using the explicit Eulerian-Lagrangian method. In the second substep, horizontal diffusion is approximated by implicit FEM in each horizontal layer. In the last substep, the continuity equation is solved by implicit FEM, and vertical diffusion and pressure gradient are discretized by implicit FDM in each nodal column. The stability analysis shows that this method is unconditionally stable. A number of numerical experiments have been performed. The results simulated by the present scheme agree well with analytical solutions and the other documented model results. The method is efficient for 3D shallow water flow computations and fully fits complicated configurations. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 837-850 
    ISSN: 0271-2091
    Keywords: dense gas dispersion ; radiation absorption ; discrete transfer method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical model is presented for the prediction of thermal radiation absorption in dense gas clouds during accidental release in the atmosphere. The model is based on the discrete transfer method (DT method) that was originally developed for modelling radiation in combustion chambers. The radiation model assumes a number of representative rays of predetermined orientation fired from each of the domain boundaries. Each ray is traced through the domain elements until reaching another boundary where it is terminated. Radiation sources are calculated for each element by performing an energy balance across each element for each ray passing through it. The energy sources recovered are fed into the finite element flow solver for every time step in the energy equation. The model proved accurate, and memory and computer time efficient. It showed that accounting for radiation effects lead to improved predictions. It also showed that in certain scenarios, radiation effects could be predominant. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 877-885 
    ISSN: 0271-2091
    Keywords: B-spline basis ; Galerkin method ; Gauss-Newton method ; mixed formulation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A mixed Galerkin technique with B-spline basis functions is presented to compute two-dimensional incompressible flow in terms of the primitive variable formulation. To circumvent the Babuska-Brezzi stability criterion, the artificial compressibility formulation of the equation of mass conservation is employed. As a result, the diagonal components of the matrix form in the governing equations are not singular. The B-spline basis is used because it is superior to other splines in providing computer solutions to fluid flow problems. One of the advantages of the B-spline basis is that it has excellent approximation properties. Numerical examples of applications of the mixed formulation are presented to demonstrate the convergence characteristics and accuracy of the present formulation. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 927-957 
    ISSN: 0271-2091
    Keywords: multigrid methods ; finite elements ; finite volumes ; semi-coarsening ; numerical analysis ; turbulent flows ; compressible flows ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Extending multigrid concepts to the calculation of complex compressible flow is usually not straightforward. This is especially true when non-embedded grid hierarchies or volume agglomeration strategies are used to construct a gradation of unstructured grids. In this work, a multigrid method for solving second-order PDE's on stretched unstructured triangulations is studied. The finite volume agglomeration multigrid technique originally developed for solving the Euler equations is used (M.-H. Lallemand and A. Dervieux, in Multigrid Methods, Theory, Applications and Supercomputing, Marcel Dekker, 337-363 (1988)). First, a directional semi-coarsening strategy based on Poisson's equation is proposed. The second-order derivatives are approximated on each level by introducing a correction factor adapted to the semi-coarsening strategy. Then, this method is applied to solve the Poisson equation. It is extended to the 2D Reynolds-averaged Navier-Stokes equations with appropriate boundary treatment for low-Reynolds number turbulent flows. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 17-37 
    ISSN: 0271-2091
    Keywords: incompressible Navier-Stokes ; parallel finite element method ; Galerkin approximation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A parallel semi-explicit iterative finite element computational procedure for modelling unsteady incompressible fluid flows is presented. During the procedure, element flux vectors are calculated in parallel and then assembled into global flux vectors. Equilibrium iterations which introduce some ‘local implicitness’ are performed at each time step. The number of equilibrium iterations is governed by an implicitness parameter. The present technique retains the advantages of purely explicit schemes, namely (i) the parallel speed-up is equal to the number of parallel processors if the small communication overhead associated with purely explicit schemes is ignored and (ii) the computation time as well as the core memory required is linearly proportional to the number of elements. The incompressibility condition is imposed by using the artificial compressibility technique. A pressure-averaging technique which allows the use of equal-order interpolations for both velocity and pressure, this simplifying the formulation, is employed. Using a standard Galerkin approximation, three benchmark steady and unsteady problems are solved to demonstrate the accuracy of the procedure. In all calculations the Reynolds number is less than 500. At these Reynolds numbers it was found that the physical dissipation is sufficient to stabilize the convective term with no need for additional upwind-type dissipation. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1003-1022 
    ISSN: 0271-2091
    Keywords: steady approach flow ; low Reynolds numbers ; 3D simulation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The three-dimensional (3D) unsteady viscous wake of a circular cylinder exposed to a steady approach flow is calculated using a fractional-step finite-difference/spectral-element method. The calculated flow fields at Reynolds numbers of 100 (2D) and 200 (3D) are examined in detail. The flow field at Re = 100 is 2D as expected, while the flow field at Re = 200 has distinct 3D features, with spanwise wavelengths of about 3.75 cylinder diameters. The calculated results produce drag and lift coefficients and Strouhal numbers that agree extremely well with the experimental values. These 3D values at Re = 200 are in better agreement with experimental values than the results of a 2D calculation at Re = 200, which is expected. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1023-1038 
    ISSN: 0271-2091
    Keywords: three-state anemometry ; velocity field ; particle motion equation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An application of a new flow measurement technique is described which allows for the non-intrusive simultaneous measurement of flow velocity, density, and viscosity. The viscosity information can be used to derive the flow field temperature. The combination of the three measured variables and the perfect-gas law then leads to an estimate of the flow field thermodynamic pressure. Thus, the instantaneous state of a flow field can be completely described. Three-state anemometry (3SA), a derivative of particle image velocimetry (PIV), which uses a combination of three monodisperse sizes of styrene seeding particles is proposed. A marker seeding is chosen to follow the flow as closely as possible, while intermediate and large seeding populations provide two supplementary velocity fields, which are also dependent on fluid density and viscosity. A simplified particle motion equation, aimed at turbomachinery applications, is then solved over the whole field to provide both density and viscosity data. The three velocity fields can be separated in a number of ways. The simplest and that proposed in this paper is to dye the different populations and view the region of interest through interferometric filters. The two critical aspects needed to enable the implementation of such a technique are a suitable selection of the diameters of the particle populations, and the separation of the velocity fields. There has been extensive work on the seeding particle behaviour which allows an estimate of the suitable particle diameters to be made. A technique is described in this paper to allow the separation of particles in a range of micrometer sized velocity fields through fluorescence (separation through intensity also being possible). Some preliminary results by direct numerical simulation (DNS) of a 3SA image are also presented. The particle sizes chosen were 1 μm and 5 μm, tested on the near-wake flow past a cylinder to investigate viscosity only, assuming uniform flow density. The accuracy of the technique, derived from simulations of swirling flows, is estimated as 0.5% RMS for velocity, 2% RMS for the density and viscosity, and 4% RMS for the temperature estimate. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1085-1105 
    ISSN: 0271-2091
    Keywords: adaptive ; hybrid grids ; incompressible ; Navier-Stokes ; finite volume ; pressure correction ; 3-D ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Hybrid grids consisting of prisms and tetrahedra are employed for the solution of the 3-D Navier-Stokes equations of incompressible flow. A pressure correction scheme is employed with a finite volume-finite element spatial discretization. The traditional staggered grid formulation has been substituted with a collocated mesh approach which uses fourth-order artificial dissipation. The hybrid grid is refined adaptively in local regions of appreciable flow variations. The scheme operations are performed on an edge-wise basis which unifies treatment of both types of grid elements. The adaptive method is employed for incompressible flows in both single and multiply-connected domains. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 199-215 
    ISSN: 0271-2091
    Keywords: air-conditioning unit ; k-∊ model ; Reynolds stress model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Details are given of a study to obtain experimental data in an idealized environment for the purpose of evaluating the corresponding computational predictions and which supplement parallel measurements made in actual packaged air-conditioning units. The system consisted of a purpose-built low-speed wind tunnel with a working section constructed to reproduce particular features of the real units. In the experiment, both the mean velocity profiles and turbulence properties of the flow are obtained from triple-hot-wire anemometry measurements. A numerical model, based on finite volume methodology, was used to obtain the solution of the Reynolds-averaged Navier-Stokes equations for incompressible isothermal flow. The Reynolds stress terms in the equations are calculated using the standard k-∊ model and second-moment closure (Reynolds stress) models. The accuracy of the two models was evaluated against the experimental measurements made 10 mm downstream of a baffle. The results show that the standard k-∊ model gave the better agreement except in regions of strong recirculation. © 1997 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 235-247 
    ISSN: 0271-2091
    Keywords: confined explosions ; risk assessment ; CFD ; adaptive mesh refinement ; multiple obstacles ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Explosion hazards constitute a significant practical problem for industry. In response to the need for better-resolved predictions for confined explosions, and particularly with a view to advancing safety cases for offshore oil and gas rigs, an existing unstructured, adaptive mesh, finite volume Reynolds-averaged Navier-Stokes computational fluid dynamics code (originally developed to handle non-combusting turbomachinery flows) has been modified to include a one-equation, eddy break-up combustion model. Two benefits accrue from the use of unstructured, solution-adaptive meshes: first, great geometrical flexibility is possible; second, automatic mesh adaptation allows computational effort to be focused on important or interesting areas of the flow by enhancing mesh resolution only where it is required. In the work reported here, the mesh was adaptively refined to achieve flame front capture, and it is shown that this results in a 10%-33% CPU saving for two-dimensional calculations and a saving of between 57% and 70% for three-dimensional calculations. The geometry of the three-dimensional calculations was relatively simple, and it may be expected that the use of unstructured meshes for truly complex geometries will result in CPU savings sufficient to allow an order-of-magnitude increase in either complexity or resolution. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 281-301 
    ISSN: 0271-2091
    Keywords: Navier-Stokes equations ; SIMPLE algorithm ; algebraic multigrid methods ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The application of standard multigrid methods for the solution of the Navier-Stokes equations in complicated domains causes problems in two ways. First, coarsening is not possible to full extent since the geometry must be resolved by the coarsest grid used. Second, for semi-implicit time-stepping schemes, robustness of the convergence rates is usually not obtained for convection-diffusion problems, especially for higher Reynolds numbers. We show that both problems can be overcome by the use of algebraic multigrid (AMG), which we apply for the solution of the pressure and momentum equations in explicit and semi-implicit time-stepping schemes. We consider the convergence rates of AMG for several model problems and demonstrate the robustiness of the proposed scheme. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 345-364 
    ISSN: 0271-2091
    Keywords: liquid-particle flow ; computational efficiency ; Eulerian-Lagrangian model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The dispersion of solid particles in a turbulent liquid flow impinging on a centrebody through an axisymmetric sudden expansion was investigated numerically using a Eulerian-Lagrangian model. Detailed experimental measurements at the inlet were used to specify the inlet conditions for two-phase flow computations. The anisotropy of liquid turbulence was accounted for using a second-moment Reynold stress transport model. A recently developed stochastic-probabilistic model was used to enhance the computational efficiency of Lagrangian trajectory computations. Numerical results of the stochastic-probabilistic model using 650 particle trajectories were compared with those of the conventional stochastic discrete-delta-function model using 18 000 particle trajectories. In addition, results of the two models were compared with experimental measurements. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 369-401 
    ISSN: 0271-2091
    Keywords: storm surge ; shallow water model ; grid convergence ; coastal ocean ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The focus of this paper is a systematic determination of the relationship between grid resolution and errors associated with computations of hurricane storm surge. A grid structure is sought that provides the spatial resolution necessary to capture pertinent storm surge physics and does not overdiscretize. A set of numerical experiments simulating storm surge generation over 14 grid discretizations of idealized domains examines the influence of grid spacing, shoreline detail, coastline resolution and characteristics of the meteorological forcing on storm surge computations. Errors associated with a given grid are estimated using a Richardson-based error estimator. Analysis of the magnitude and location of estimated errors indicates that underresolution on the continental shelf leads to significant overprediction of the primary storm surge. In deeper waters, underresolution causes smearing or damping of the inverted barometer forcing function, which in turn results in underprediction of the surge elevation. In order to maintain a specified error level throughout the duration of the storm, the highest grid resolution is required on the continental shelf and particularly in nearshore areas. The disparity of discretization requirements between deep waters and coastal regions is best met using a graded grid. Application of the graded gridding strategy to the hindcast of Hurricane Camille reinforces the necessity of using a grid that has high levels of resolution in nearshore regions and areas of complex coastal geometry. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 27 (1998), S. 127-138 
    ISSN: 0271-2091
    Keywords: compressible flow ; supersonic flows ; aerofoils ; Cauchy/Riemann equations ; Crocco's relation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper, alternative formulations of the steady Euler equations for conservation of mass, momentum and energy are adopted for the numerical simulation of compressible flows with shock waves. The total enthalpy is assumed to be constant and hence an isentropic density is calculated in terms of the velocity components. Also, the x- and y-momentum equations written in conservation form are combined to yield the tangential and normal momentum equations. For smooth flows the tangential momentum equation reduces to the entropy transport equation, while the normal momentum equation gives the vorticity in terms of the entropy gradient normal to the flow direction (Crocco's relation). Hence the velocity components can be obtained from the continuity equation and normal momentum equation (Cauchy/Riemann equations), while the entropy correction for the density is obtained from the tangential momentum equation (this correction is not needed in the isentropic flow regions). The present formulation can be easily extended to handle variable total enthalpy. Preliminary results are presented for transonic and supersonic flows over aerofoils and the entropy and vorticity effects are clearly identified. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 27 (1998), S. 139-157 
    ISSN: 0271-2091
    Keywords: hydrodynamic stability ; finite element method ; incompressible cavity flow ; Arnold's method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Numerical methods have been applied to theoretical studies of instability and transition to turbulence. In this study an analysis of the linear stability of incompressible flow is undertaken. By means of the finite element method the two-dimensional base flow is computed numerically over a range of Reynolds numbers and is perturbed with three-dimensional disturbances. The partial differential equations governing the evolution of perturbation are obtained from the non-linear Navier-Stokes equations with a slight compressibility by using linear stability and normal mode analysis. In terms of the finite element discretization a non-singular generalized eigenproblem is formulated from these equations whose solution gives the dispersion relation between complex growth rate and wave number. This study presents stability curves to identify the critical Reynolds number and critical wavelength of the neutral mode and discusses the mechanism of instability. The stability of lid-driven cavity flow is examined. Taylor-Göertler-like vortices in the cavity are obtained by means of reconstruction of three-dimensional flows. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 519-531 
    ISSN: 0271-2091
    Keywords: wavy channel flow ; peristaltic motion ; spectral collocation method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical procedure is developed for the analysis of flow in a channel whose walls describe a travelling wave motion. Following a perturbation method, the primitive variables are expanded in a series with the wall amplitude as the perturbation parameter. The boundary conditions are applied at the mean surface of the channel and the first-order perturbation quantities are calculated using the pseudospectral collocation method. Although limited by the linear analysis, the present approach is not restricted by the Reynolds number of the flow and the wave number and frequency of the wavy-walled channel. Using the computed wall shear stresses, the positions of flow separation and reattachment are determined. The variations in velocity and pressure with frequency of excitation are also presented. © 1998 John Wiley & Sons, Ltd.
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  • 62
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    International Journal for Numerical Methods in Fluids 27 (1998), S. 207-227 
    ISSN: 0271-2091
    Keywords: directional solidification ; multicomponent alloys ; dendritic monocrystals ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A finite element model of dendritic solidification of multicomponent alloys is presented that includes solutal convection and is an extension of a previously developed model for solidification of binary alloys. The model is applied to simulation of the solidification of ternary and quaternary Ni-based alloys. The role of solutal convection in the macrosegregation and the formation of freckles is analysed. Calculations show the effects of geometry and material properties on the convection patterns and the attendant segregation. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 27 (1998), S. 1-11 
    ISSN: 0271-2091
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: No Abstract
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  • 64
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 157-186 
    ISSN: 0271-2091
    Keywords: advective transport ; semi-implicit ; conservative ; unconditionally stable ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A one-dimensional scalar transport method which is appropriate for simulations over a wide range of Courant number is described. Von Neumann stability and matrix invertibility are guaranteed for all Courant numbers and the method has less diffusive and dispersive error than simpler implicit methods. It is implemented for vertical scalar transport in a three-dimensional hydrodynamic model, with horizontal transport discretized explicitly. The method is applied and compared with simpler semi-implicit methods in several test cases and used for a simulation of scalar transport in an estuary. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 23-46 
    ISSN: 0271-2091
    Keywords: domain decomposition ; parallel algorithms ; finite element ; Lagrange multipliers ; projected GMRES ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A parallel solver based on domain decomposition is presented for the solution of large algebraic systems arising in the finite element discretization of mechanical problems. It is hybrid in the sense that it combines a direct factorization of the local subdomain problems with an iterative treatment of the interface system by a parallel GMRES algorithm. An important feature of the proposed solver is the use of a set of Lagrange multipliers to enforce continuity of the finite element unknowns at the interface. A projection step and a preconditioner are proposed to control the conditioning of the interface matrix.The decomposition of the finite element mesh is formulated as a graph partitioning problem. A two-step approach is used where an initial decomposition is optimized by non-deterministic heuristics to increase the quality of the decomposition.Parallel simulations of a Navier-Stokes flow problem carried out on a Convex Exemplar SPP system with 16 processors show that the use of optimized decompositions and the preconditioning step are keys to obtaining high parallel efficiencies. Typical parallel efficiencies range above 80%. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 47-72 
    ISSN: 0271-2091
    Keywords: large eddy simulation ; juncture flows ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Large eddy simulation (LES) results are reported for temporally developing solid-solid and solid-rigid-lid juncture flows. A MacCormack-type scheme that is second-order in time, and fourth-order in space for the convective terms and second-order in space for the viscous terms, is used. The simulations are obtained for a low subsonic Mach number. The subgrid-scale stresses (SGS) are modeled using the dynamic modeling procedure. The turbulent flow field generated on a flat-plate boundary layer is used to initialize the juncture flow simulations. The results of the flat-plate boundary layer simulations are validated with experimental and direct numerical simulations (DNS) data. In juncture flow simulations, the presence of an adjacent solid-wall/rigid-lid boundary altered the mean and the turbulent field, setting up gradients in the anisotropy of normal Reynolds stresses resulting in the formation of turbulence-induced secondary vortices. The relative size of these secondary vortices and the distribution of mean and turbulent quantities are in qualitative agreement with the experimental observations for the solid-solid juncture. The overall distribution of the mean and turbulence quantities showed close resemblance between the solid-solid and the solid-rigid-lid junctures; except for the absence of a second vortical region near the rigid-lid boundary. In agreement with the experimental observations, it was found that the normalized anisotropy term exhibited similarity when plotted against the distance from the boundary, regardless of the type of boundary, i.e. solid-wall or rigid-lid. The turbulent kinetic energy increased near the rigid-lid boundary. While the surface normal velocity fluctuations decreased to zero at the rigid-lid boundary, the other two velocity components showed an increase in their energy, which is also consistent with the experimental observations. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 113-128 
    ISSN: 0271-2091
    Keywords: optimal control ; Burgers' equation ; data assimilation ; adjoint model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to use the optimal control techniques in models of geophysical flow circulation, an application to a 1D advection-diffusion equation, the so-called Burgers' equation, is described. The aim of optimal control is to find the best parameters of the model which ensure the closest simulation to the observed values. In a more general case, the continuous problem and the corresponding discrete form are formulated. Three kinds of simulation are realized to validate the method. Optimal control processes by initial and boundary conditions require an implicit discretization scheme on the first time step and a decentered one for the non-linear advection term on boundaries. The robustness of the method is tested with a noised dataset and random values of the initial controls. The optimization process of the viscosity coefficient as a time- and space-dependent variable is more difficult. A numerical study of the model sensitivity is carried out. Finally, the numerical application of the simultaneous control by the initial conditions, the boundary conditions and the viscosity coefficient allows a possible influence between controls to be taken into account. These numerical experiments give methodological rules for applications to more complex situations. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 143-156 
    ISSN: 0271-2091
    Keywords: turbine ; spiral casing ; finite element method ; Galerkin weighted residual technique ; Gauss-Legendre quadrature ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Flow through the spiral casing of a hydraulic turbine was analyzed. Reynolds averaged Navier-Stokes equations were solved using a finite element method. The physical domain was divided into a number of hexahedral elements which are isoparametrically mapped onto standard cubic elements. Numerical integration for the unsteady momentum equation is performed over such hexahedral elements to obtain a provisional velocity field. Compliance with the mass conservation equation and determination of the pressure correction are accomplished through an iterative procedure. The velocity distribution inside the spiral casing corroborates the results available in literature. The static pressure at the midplane generally decreases from the outside wall towards the exit of the spiral casing. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 201-213 
    ISSN: 0271-2091
    Keywords: curved surface ; shallow water ; non-hydrostatic ; spillway ; finite element ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In Part I a detailed derivation of a more general shallow water equation set was developed via a perturbation analysis. A finite element computational model of these more general equations is now constructed and the model behavior is compared with conventional shallow water formulations applied to an outletworks flume. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 225-242 
    ISSN: 0271-2091
    Keywords: turbulent flow ; non-linear turbulence modelling ; secondary flow ; rectangular duct ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Details of the turbulent flow in a 1:8 aspect ratio rectangular duct at a Reynolds number of approximately 5800 were investigated both numerically and experimentally. The three-dimensional mean velocity field and the normal stresses were measured at a position 50 hydraulic diameters downstream from the inlet using laser doppler velocimetry (LDV). Numerical simulations were carried out for the same flow case assuming fully developed conditions by imposing cyclic boundary conditions in the main flow direction. The numerical approach was based on the finite volume technique with a non-staggered grid arrangement and the SIMPLEC algorithm. Results have been obtained with a linear and a non-linear (Speziale) k-ε model, combined with the Lam-Bremhorst damping functions for low Reynolds numbers. The secondary flow patterns, as well as the magnitude of the main flow and overall parameters predicted by the non-linear k-ε model, show good agreement with the experimental results. However, the simulations provide less anisotropy in the normal stresses than the measurements. Also, the magnitudes of the secondary velocities close to the duct corners are underestimated. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 317-336 
    ISSN: 0271-2091
    Keywords: algebraic multigrid ; elementary restriction/prolongation ; minimum residual methods ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An algebraic multigrid (AMG) scheme is presented for the efficient solution of large systems of coupled algebraic equations involving second-order discrete differentials. It is based on elementary (zero-order) intergrid transfer operators but exhibits convergence rates that are independent of the system bandwidth. Inconsistencies in the coarse-grid approximation are minimised using a global scaling approximation which requires no explicit geometrical information. Residual components of the error spectrum that remain poorly represented in the coarse-grid approximations are reduced by exploiting Krylof subspace methods. The scheme represents a robust, simple and cost-effective approach to the problem of slowly converging eigenmodes when low-order prolongation and restriction operators are used in multigrid algorithms. The algorithm investigated here uses a generalised conjugate residual (GCR) accelerator; it might also be described as an AMG preconditioned GCR method. It is applied to two test problems, one based on a solution of a discrete Poisson-type equation for nodal pressures in a pipe network, the other based on coupled solutions to the discrete Navier-Stokes equations for flows and pressures in a driven cavity. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 293-315 
    ISSN: 0271-2091
    Keywords: Euler equations ; free surface ; gravity waves ; finite volume method ; fractional step method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A fractional step method is developed for solving the time dependent two-dimensional Euler equations with full non-linear free-surface boundary conditions. The geometry of the free surface is described by a height function, and its evolution is tracked by integrating in time the kinematic boundary conditions based on the free-surface volume flux. The fluid domain is discretised by adapting a time-varying curvilinear grid to all boundaries, including the free surface. Mass and momentum equations are discretised by a conservative finite volume formulation, taking into account the time dependency of the grid. A fractional step type method is developed for integrating the fluid motion in time. The method is applied to a non-linear standing wave in a square container, testing for compliance with mass and energy conservation and comparing computed wave period with other results. Non-linear travelling waves are simulated in channels with either constant depth or varying depth and non-linear wave processes involving both triad interactions and quartet interactions are studied. Results are compared with both experimental data and theoretical results and excellent agreement is found. Interaction of waves and currents is studied. The blocking of waves in an opposing current is simulated and found to show good agreement with theoretical results. The method is intended to be a first step towards a full description of wave dynamics interacting with structures and currents. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 395-418 
    ISSN: 0271-2091
    Keywords: compressible liquid ; Riemann solvers ; approximate Riemann solvers ; Tammann equation of state ; Tait equation of state ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A number of Riemann solvers are proposed for the solution of the Riemann problem in a compressible liquid. Both the Tait and Tammann equations of state are used to describe the liquid. Along with exact Riemann solvers, a detailed description of a primitive variable Riemann solver, a two-shock Riemann solver, a two-rarefaction Riemann solver and an extension to the HLL Riemann solver, namely the HLLC Riemann solver, are presented. It is shown how these Riemann solvers may be implemented into Godunov-type numerical methods. The appropriateness of each of the Riemann solvers for a number of flow situations is demonstrated by applying Godunov's method to some revealing shock tube test problems. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 419-442 
    ISSN: 0271-2091
    Keywords: finite element analysis ; design sensitivity analysis ; optimization ; mold filling ; free surface ; turbulence ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A novel, fully-analytical design sensitivity formulation for transient, turbulent, free surface flows is derived and implemented in the context of finite element analysis. The time-averaged, turbulent form of the Navier-Stokes equations are solved using a mixing length model, in conjunction with the volume of fluid (VOF) method to model the free surface movement. The design derivatives of these governing equations are computed and solved to find the analytical sensitivities of the fluid position, velocity and pressure fields with respect to shape design variables. The computational efficiency produced by evaluating the sensitivities analytically is demonstrated. The design of the runner and gating system of a simple block casting is presented as an example application for using sensitivity information in design. The analytical sensitivity routine is coupled to a numerical optimizer to yield an automated method for optimal design of the casting rigging system. The results produce runner shapes which eliminate mold-gas aspiration. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 477-499 
    ISSN: 0271-2091
    Keywords: natural convection ; tilted cavity ; partial cooling ; storage tanks ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Two-dimensional numerical simulations of laminar natural convection in a partially cooled, differentially heated inclined cavities are performed. One of the cavity walls is entirely heated to a uniformly high temperature (heat source) while the opposite wall is partially cooled to a lower temperature (heat sink). The remaining walls are adiabatic. The tilt angle of the cavity is varied from 0° (heated from left) to -90° (heated from top). The fast false implicit transient scheme (FITS) algorithm, developed earlier by the same authors, is modified to solve the derived variables vorticity-streamfunction formulation. The effects of aspect ratio (AR), sink-source ratio and tilt angle on the average Nusselt number are examined through a parametric study; solutions are obtained for two Grashof numbers, 105 and 107. Flow patterns and isotherms are used to investigate the heat transfer and fluid flow mechanisms inside the cavity. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 523-540 
    ISSN: 0271-2091
    Keywords: non-reflecting boundary conditions ; numerical simulation ; compression wave ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In simulations of propagating blast waves the effects of artificial reflections at open boundaries can seriously degrade the accuracy of the computations. In this paper, a boundary condition based on a local approximation by a plane traveling wave is presented. The method yields small artificial reflections at open boundaries. The derivation and the theory behind these so-called plane-wave boundary conditions are presented. The method is conceptually simple and is easy to implement in two and three dimensions. These non-reflecting boundary conditions are employed in the three-dimensional computational fluid dynamics (CFD) solver FLACS, capable of simulating gas explosions and blast-wave propagation in complex geometries. Several examples involving propagating waves in one and two dimensions, shock tube and an example of a simulation of a propagating blast wave generated by an explosion in a compressor module are shown. The numerical simulations show that artificial reflections due to the boundary conditions employed are negligible. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 565-568 
    ISSN: 0271-2091
    Keywords: fundamental solution method ; integral equation method ; Navier-Stokes equations ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A complete boundary integral formulation for incompressible Navier-Stokes equations with time discretization by operator splitting is developed using the fundamental solutions of the Helmholtz operator equation with different order. The numerical results for the lift and the drag hysteresis associated with a NACA0012 aerofoil oscillating in pitch show good agreement with available experimental data. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 719-736 
    ISSN: 0271-2091
    Keywords: front tracking ; mesh adaptation ; finite element method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical model is developed for the simulation of moving interfaces in viscous incompressible flows. The model is based on the finite element method with a pseudo-concentration technique to track the front. Since a Eulerian approach is chosen, the interface is advected by the flow through a fixed mesh. Therefore, material discontinuity across the interface cannot be described accurately. To remedy this problem, the model has been supplemented with a local mesh adaptation technique. This latter consists in updating the mesh at each time step to the interface position, such that element boundaries lie along the front. It has been implemented for unstructured triangular finite element meshes. The outcome of this technique is that it allows an accurate treatment of material discontinuity across the interface and, if necessary, a modelling of interface phenomena such as surface tension by using specific boundary elements. For illustration, two examples are computed and presented in this paper: the broken dam problem and the Rayleigh-Taylor instability. Good agreement has been obtained in the comparison of the numerical results with theory or available experimental data. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 601-616 
    ISSN: 0271-2091
    Keywords: turbulence modeling ; CFD ; finite volume method ; vortex shedding ; two-layer approach ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents the results of numerical simulations of vortex shedding past a free-standing square cylinder at ReD=22 000, obtained with different turbulence models. Using wall functions, the standard k-ε model is compared with a modification suggested by Kato and Launder (Proc. 9th Symp. Turbulent Shear Flows, Kyoto, 10-4-1 (1993)). In addition, both versions are used in a two-layer approach, in which the flow close to the cylinder is computed with a locally more suitable one-equation turbulence model and only outside the viscous near-wall layer with the two mentioned high-Re model versions. To allow a comparison, the simulations are performed first using the same computational domain and boundary conditions as in previous investigations. Then results are presented that were obtained on a computational domain and with boundary conditions more suitable for a comparison with the experiments. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1155-1180 
    ISSN: 0271-2091
    Keywords: Navier-Stokes equations ; averaged volume transport equations ; void wave propagation speed ; interfacial effects ; two-phase flow ; finite difference method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A one-dimensional, time-dependent, isothermal, incompressible, Newtonian fluid, two-phase volume averaging model was developed to study momentum interaction effects in vertical ducts with bubble flow regime. For the evaluation of averaged description, potential inviscid flow around bubbles was considered in order to get closure relationships. The linear dynamic analysis is based on the eigenvalue technique, determining the domain of the hyperbolic behavior and the void fraction wave velocity, which are compared with previous models and experimental data. The solution to the partial differential equations is based on the finite difference technique implicit scheme. These schemes serve to demonstrate the numerical solution procedure. The numerical results are compared with analytical solution and experimental data for void fraction wave propagation. The importance of the surface tension effect in the behavior of the phases in transient conditions is shown. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1181-1203 
    ISSN: 0271-2091
    Keywords: trapezoidal cylinder ; laminar flow ; Reynolds number ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Characteristics of the developing recirculation region behind a tapered trapezoidal cylinder and its interaction with the separating shear layer from the leading edges were studied numerically for an impulsively started laminar flow. An unsteady stream function-vorticity formulation was used. The Reynolds numbers considered range from 25 to 1000. Pressure contours, surface pressure coefficient, wake length and drag coefficient were studied through the streamline flow field. Main flow and subflow regimes were identified by an analysis of the evolution of the flow characteristics. It was found that typically, for a given trapezoidal cylinder, flow starts with no separation. As time advances, the symmetrical standing zone of recirculation develops aft of the trapezoidal cylinder. The rate of growth in width, length and structure of the aft end eddies depends on the Reynolds number. In time, separated flow from the leading edges of the trapezoidal cylinder also develops and forms growing separation bubbles on the upper and lower inclined surfaces of the trapezoidal cylinder. As time advances, the separation bubbles on the upper and lower inclined surfaces of the cylinder grow towards the downstream regions and eventually merge with the swelling symmetrical eddies aft of the cylinder. This merging of the flows creates a complex flow regime with a disturbed tertiary flow zone near the merging junction. Eventually, depending on the Reynolds number and the tapered angle of the trapezoidal cylinder, the flow develops into a specific category of symmetrical standing recirculatory flow with its own distinct characteristics. Comparisons with the available results of other investigators showed very good agreement. © 1998 John Wiley & Sons, Ltd.
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  • 82
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    International Journal for Numerical Methods in Fluids 27 (1998), S. 33-39 
    ISSN: 0271-2091
    Keywords: error estimation ; Stokes flow ; adaptivity ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We describe in this paper an algebraic technique for estimating local and pollution errors in finite element approximations of Stokesian flows. © 1998 John Wiley & Sons, Ltd.
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  • 83
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1053-1071 
    ISSN: 0271-2091
    Keywords: turbulence modeling ; internal flow ; flow separation ; shock-boundary layer interaction ; finite volume method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The existence of shock-turbulent boundary layer interactions lead to very complicated flow phenomena and pose a challenge for numerical simulation. In this paper, two turbulence models, the Baldwin-Lomax (B-L) model and the Johnson-King (J-K) model, which were originally developed for simple external flow simulation, are modified to model complex high-speed internal separated flows. The full Navier-Stokes solver used in this paper is based on a cell-centered finite volume method and multistepping time marching scheme. Both implicit residual smoothing and local time stepping techniques are incorporated to accelerate the convergence rate. To ensure the numerical stability with the present explicit scheme, a point-implicit treatment to the source term in the ordinary differential equation (ODE) of the J-K model has been developed and has proved to be very effective in modeling such a complex flow. An arc-bump channel flow case has been studied. Comparisons of computed results with experimental data show that the present solver, with the modified turbulence models, predicts the shock and the flow separation very well. The J-K model is found to predict the size of the separation bubble with a higher accuracy. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1093-1108 
    ISSN: 0271-2091
    Keywords: boundary conditions ; Euler equations ; finite volume ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The implementation of boundary conditions at rigid, fixed wall boundaries in inviscid Euler solutions by upwind, finite volume methods is considered. Some current methods are reviewed. Two new boundary condition procedures, denoted as the symmetry technique and the curvature-corrected symmetry technique are then presented. Their behaviour in relation to the problem of the subsonic flow about blunt and slender elliptic bodies is analysed. The subsonic flow inside the Stanitz elbow is then computed. The symmetry technique is proven to be as accurate as one of the current methods, second-order pressure extrapolation technique. Finally, for arbitrary curved geometries, dramatic advantages of the curvature-corrected symmetry technique over the other methods are shown. © 1998 John Wiley & Sons, Ltd.
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  • 85
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1139-1158 
    ISSN: 0271-2091
    Keywords: non-linear Reynolds stresses ; k-ε turbulence model ; higher-order convective scheme ; pressure correction ; direct sparse matrix solver ; incompressible duct flows ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A non-linear modelling of the Reynolds stresses has been incorporated into a Navier-Stokes solver for complex three-dimensional geometries. A k-ε model, adopting a modelling of the turbulent transport which is not based on the eddy viscosity, has been written in generalised co-ordinates and solved with a finite volume approach, using both a GMRES solver and a direct solver for the solution of the linear systems of equations. An additional term, quadratic in the main strain rate, has been introduced into the modelling of the Reynolds stresses to the basic Boussinesq's form; the corresponding constant has been evaluated through comparison with the experimental data. The computational procedure is implemented for the flow analysis in a 90° square section bend and the obtained results show that with the non-linear modelling a much better agreement with the measured data is obtained, both for the velocity and the pressure. The importance of the convection scheme is also discussed, showing how the effect of the non-linear correction added to the Reynolds stresses is effectively hidden by the additional numerical diffusion introduced by a low-order convection scheme as the first-order upwind scheme, thus making the use of higher order schemes necessary. © 1998 John Wiley & Sons, Ltd.
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  • 86
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1421-1440 
    ISSN: 0271-2091
    Keywords: parallel ; conjugate gradient ; least squares ; FEM ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this study we consider parallel conjugate gradient solution of sparse systems arising from the least-squares mixed finite element method. Of particular interest are transport problems involving convection. The least-squares approach leads to a symmetric positive system and the conjugate gradient scheme is directly applicable. The scheme is applied to both the convection-diffusion equation and to the stationary Navier-Stokes equations. Here we demonstrate parallel solution and performance studies for a representative MIMD parallel computer with hypercube architecture. © 1998 John Wiley & Sons, Ltd.
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  • 87
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1217-1239 
    ISSN: 0271-2091
    Keywords: multiphase ; multifluid ; multigrid ; FAS ; local coupled solver ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In recent years multigrid algorithms have been applied to increasingly difficult systems of partial differential equations and major improvements in both speed of convergence and robustness have been achieved. Problems involving several interacting fluids are of great interest in many industrial applications, especially in the process and petro-chemical sectors. However, the multifluid version of the Navier-Stokes equations is extremely complex and represents a challenge to advanced numerical algorithms. In this paper, we describe an extension of the full approximation storage (FAS) multigrid algorithm to the multifluid equations. A number of special issues had to be addressed. The first was the development of a customised, non-linear, coupled relaxation scheme for the smoothing step. Automatic differentiation was used to facilitate the coding of a robust, globally convergent quasi-Newton method. It was also necessary to use special inter-grid transfer operators to maintain the realisability of the solution. Algorithmic details are given and solutions for a series of test problems are compared with those from a widely validated, commercial code. The new approach has proved to be robust; it achieves convergence without resorting to specialised initialisation methods. Moreover, even though the rate of convergence is complex, the method has achieved very good reduction factors: typically five orders of magnitude in 50 cycles. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1265-1280 
    ISSN: 0271-2091
    Keywords: momentum interpolation ; contravariant velocity fluxes ; general curvilinear co-ordinates ; non-staggered grid ; lid-driven cavity flow ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An investigation has been conducted to determine the effect of the grid non-orthogonality on the convergence behavior of two-dimensional lid-driven cavity flows. The relevant theory is presented in this article. In the present work, the contravariant velocity fluxes are used as the dependent variables on non-orthogonal, non-staggered grids. The momentum equations retain a strongly conservative form. Two practices for treating the momentum interpolation method in general curvilinear co-ordinates are presented. In each practice, the momentum interpolation formulations with and without velocity underrelaxation factor are considered. The discretization equations are solved using the SIMPLE, SIMPLEC and SIMPLER algorithms. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1281-1302 
    ISSN: 0271-2091
    Keywords: large eddy simulation ; turbulent flow ; circular cylinder ; accuracy ; finite volume method ; subgrid scale model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The turbulent flow past a circular cylinder (Re=3900) was computed by large eddy simulation (LES). The objective was not to investigate the physical phenomena of this flow in detail but to study numerical and modeling aspects which influence the quality of LES solutions. Concerning the numerical method, the most important component is the discretization of the non-linear convective fluxes. Five different schemes were investigated. Also, the influence of different grid resolutions was examined. Two aspects play an important role on the modeling side, namely the near-wall model and the subgrid scale model. Owing to the restriction to low Reynolds numbers in this study, no-slip boundary conditions were used at solid walls. Therefore, only the second aspect was taken into account. Two different subgrid scale models were applied. Additionally, LES computations without any subgrid scale modeling were carried out in order to prove the performance of the models. The results were evaluated by comparison with available experimental data. © 1998 John Wiley & Sons, Ltd.
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  • 90
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1303-1324 
    ISSN: 0271-2091
    Keywords: grid generation ; automation ; Cartesian ; diagonal ; saw-tooth ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A method of automatic grid generation for complex boundaries in Cartesian co-ordinates is proposed in this paper. In addition to the Cartesian grid lines the diagonal segments are used for the approximations of complex geometries in Cartesian co-ordinates. A structured Cartesian grid is employed for the sake of the numerical simplicity and the potential of automatic grid generation. The automatic grid generation is achieved by this diagonal Cartesian method and the accuracy estimations of geometry approximations are given. The approximations of a few complex geometries, such as the multibody system in porous media, lake banks, grooved channels and spheres are shown and analyzed. The proposed method is verified by the numerical solutions of a rotated cavity flow. It is shown that the diagonal Cartesian method improves both the accuracy of geometry approximations and the numerical solution of a rotated cavity flow, comparing with the traditional saw-tooth method in which only Cartesian grid lines are utilized for geometry approximations. The stability and convergence of the proposed method is demonstrated. Finally, the application of the diagonal Cartesian method for the prediction of a grooved channel flow is presented. © 1998 John Wiley & Sons, Ltd.
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  • 91
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1355-1369 
    ISSN: 0271-2091
    Keywords: viscous flow ; moving boundary ; fountain flow ; pseudo-concentration method ; finite element method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Mould filling processes, in which a material flow front advances through a mould, are typical examples of moving boundary problems. The moving boundary is accompanied by a moving contact line at the mould walls causing, from a macroscopic modelling viewpoint, a stress singularity. In order to be able to simulate such processes, the moving boundary and moving contact line problem must be overcome. A numerical model for both two- and three-dimensional mould filling simulations has been developed. It employs a pseudo-concentration method in order to avoid elaborate three-dimensional remeshing, and has been implemented in a finite element program. The moving contact line problem has been overcome by employing a Robin boundary condition at the mould walls, which can be turned into a Dirichlet (no-slip) or a Neumann (free-slip) boundary condition depending on the local pseudo-concentration. Simulation results for two-dimensional test cases demonstrate the model's ability to deal with flow phenomena such as fountain flow and flow in bifurcations. The method is by no means limited to two-dimensional flows, as is shown by a pilot simulation for a simple three-dimensional mould. The reverse problem of mould filling is the displacement of a viscous fluid in a tube by a less viscous fluid, which has had considerable attention since the 1960's. Simulation results for this problem are in good agreement with results from the literature. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1441-1479 
    ISSN: 0271-2091
    Keywords: gas-solid particle flow ; dilute to dense concentrations ; two-fluid model ; kinetic theory ; control-volume finite element method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A two-fluid model of gas-solid particle flows that is valid for a wide range of the solid-phase volume concentration (dilute to dense) is presented. The governing equations of the fluid phase are obtained by volume averaging the Navier-Stokes equations for an incompressible fluid. The solid-phase macroscopic equations are derived using an approach that is based on the kinetic theory of dense gases. This approach accounts for particle-particle collisions. The model is implemented in a control-volume finite element method for simulations of the flows of interest in two-dimensional, planar or axisymmetric, domains. The chosen mathematical model and the proposed numerical method are applied to three test problems and one demonstration problem. © 1998 John Wiley & Sons, Ltd.
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  • 93
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1199-1216 
    ISSN: 0271-2091
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Several computational methods to aid analysis of steady state problems in fluid dynamics are demonstrated. These include tracking of selected flow states; computing linearized parameter sensitivities and frequency response to forced parameter perturbations; and determining the topology of a flow by systematically locating critical points of the velocity vector field. The primary concern addressed by these methods is analysis of collections of steady state solutions obtained through parameter studies, rather than analysis of an isolated solution. In this regard, these methods are intended to answer the criticism sometimes made that solutions obtained by numerical methods do not lend insight to parameter effects so easily as do traditional methods. Dip coating, slot coating, and a prototype of forward roll coating (a lid-driven cavity with throughflow) are used to demonstrate application of the methods. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 28 (1998), S. 1325-1353 
    ISSN: 0271-2091
    Keywords: finite elements ; compressible flow ; artificial viscosity ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The performance of different shock capturing viscosities has been examined using our general fluid mechanics algorithm. Four different schemes have been tested, both for viscous and inviscid compressible flow problems. Results show that the methods based on the second gradient of pressure give better performance in all situations. For instance, the method constructed from the nodal pressure values and consistent and lumped mass matrices is an excellent choice for inviscid problems. The method based on L2 projection is better than any other method in viscous flow computations. The residual based anisotropic method gives excellent performance in the supersonic range and gives better results in the hypersonic regime if a small amount of residual smoothing is used. © 1998 John Wiley & Sons, Ltd.
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  • 95
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1-16 
    ISSN: 0271-2091
    Keywords: finite difference schemes ; boundedness property ; convection-diffusion problems ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new scheme for convection term discretization is developed, called VONOS (variable-order non-oscillatory scheme). The development of the scheme is based on the behaviour of well-known non-oscillatory schemes in the pure convection of a step profile test case. The new scheme is a combination of the QUICK and BSOU (bounded second-order upwind) schemes. These two schemes do not have the same formal order of accuracy and for that reason the formal order of accuracy of the new scheme is variable. The scheme is conservative, bounded and accurate. The performance of the new scheme was assessed in three test cases. The results showed that it is more accurate than currently used higher-order schemes, so it can be used in a general purpose algorithm in order to save computational time for the same level of accuracy. © 1998 John Wiley & Sons, Ltd.
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  • 96
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 959-975 
    ISSN: 0271-2091
    Keywords: grid adaption ; grid iterations ; iterative solvers ; operator splitting ; finite elements ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Solution algorithms for solving the Navier-Stokes equations without storing equation matrices are developed. The algorithms operate on a nodal basis, where the finite element information is stored as the co-ordinates of the nodes and the nodes in each element. Temporary storage is needed, such as the search vectors, correction vectors and right hand side vectors in the conjugate gradient algorithms which are limited to one-dimensional vectors. The nodal solution algorithms consist of splitting the Navier-Stokes equations into equation systems which are solved sequencially. In the pressure split algorithm, the velocities are found from the diffusion-convection equation and the pressure is computed from these velocities. The computed velocities are then corrected with the pressure gradient. In the velocity-pressure split algorithm, a velocity approximation is first found from the diffusion equation. This velocity is corrected by solving the convection equation. The pressure is then found from these velocities. Finally, the velocities are corrected by the pressure gradient. The nodal algorithms are compared by solving the original Navier-Stokes equations. The pressure split and velocity-pressure split equation systems are solved using ILU preconditioned conjugate gradient methods where the equation matrices are stored, and by using diagonal preconditioned conjugate gradient methods without storing the equation matrices. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 39-56 
    ISSN: 0271-2091
    Keywords: square cylinder ; incompressible flow ; laminar vortex shedding ; angle of incidence ; onset of vortex shedding ; blockage ; open boundary condition ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Calculations of unsteady 2D flow around a square cylinder at incidence (α=0°-45°) are presented. The Reynolds numbers are low (Re=45-200) so that the flow is presumably laminar. A von Kármán vortex sheet is predicted behind the cylinders with a periodicity which agrees well with experiments. An incompressible SIMPLEC code is used with a non-staggered grid arrangement. A third-order QUICK scheme is used for the convective terms. The time discretization is implicit and a second-order Crank-Nicolson scheme is employed. At the outlet of the computational domain a convective Sommerfeld boundary condition is compared with a traditional Neumann condition. The convective boundary condition is shown to be more effective in reducing the CPU time, reducing the upstream influence of the outlet and thus reducing the necessary downstream extent of the domain. A study of the effects of spatial resolution and blockage is also provided. The onset of vortex shedding is investigated by using the Stuart-Landau equation at various angles of incidence and for a solid blockage of 5%. A number of quantities such as Strouhal number and drag, lift and moment coefficients are calculated. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 125-143 
    ISSN: 0271-2091
    Keywords: Navier-Stokes ; unsteady separated flow ; laminar flow ; vorticity ; non-inertial frame ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A vorticity velocity formulation is proposed for the solution of the equations for viscous flow around a moving profile. A non-inertial reference frame is used and the velocities are computed from a Poincaré integral formula. The studies are directed towards the need to understand helicopter blade aerodynamics. Worked examples are given which validate the method and programme for laminar flows, at least for low Reynolds numbers. © 1998 John Wiley & Sons, Ltd.
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  • 99
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 145-175 
    ISSN: 0271-2091
    Keywords: effective property ; porous media ; sedimentation ; finite element ; Stokes flow ; variational bounds ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We present an analytico-computational methodology for the prediction of the effective properties of two types of three-dimensional particulate Stokes flows: porous media and sedimentation flows. In particular, we determine the permeability and average settling rate of media that consist of non-colloidal monodisperse solid spherical particles immersed in a highly viscous Newtonian fluid. Our methodology recasts the original problem into three scale-decoupled subproblems: the macro-, meso- and microscale subproblems. In the macroscale analysis the appropriate effective property is used to calculate the bulk quantity of interest. The mesoscale problem provides this effective property through the finite element solution of the transport equations in a periodic cell containing many particles distributed according to a prescribed joint probability density function. Finally, the microscale analysis allows us to accommodate mesoscale realizations in which two or more inclusions are in very close proximity; this geometrical stiffness is alleviated by introducing simple domain modifications that relax the mesh generation requirements while simultaneously yielding rigorous bounds for the effective property. Our methodology can treat random particle distributions as well as regular arrays; in the current paper we analyse only the latter. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical Methods in Fluids 26 (1998), S. 1107-1123 
    ISSN: 0271-2091
    Keywords: computational aeroacoustics ; radiation boundary conditions ; scattering of sound or vorticity waves ; high-order finite difference solutions ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A set of non-homogeneous radiation and outflow boundary conditions which automatically generate prescribed incoming acoustic or vorticity waves and, at the same time, are almost transparent to outgoing sound waves produced internally in a finite computation domain is proposed. This type of boundary condition is needed for the numerical solution of many exterior aeroacoustics problems. In computational aeroacoustics, the computation scheme must be as non-dispersive and non-dissipative as possible. It must also support waves with wave speeds which are nearly the same as those of the original linearized Euler equations. To meet these requirements, a high-order/large-stencil scheme is often necessary. The proposed non-homogeneous radiation and outflow boundary conditions are designed primarily for use in conjunction with such high-order/large-stencil finite difference schemes. © 1998 John Wiley & Sons, Ltd.
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