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  • 2010-2014  (152)
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  • 2012  (152)
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  • 1
    Publication Date: 2021-05-19
    Description: Il est connu que les ports soumis à un trafic maritime intense réceptionnent éventuellement les eaux de ballast des navires en provenance de diverses contrées océaniques. De part le monde, le transfert et l’invasion de plusieurs espèces nuisibles via le déversement des eaux de ballast et le fouling des coques des navires ont été amplement mis en cause ces derniers temps. Ces introductions peuvent causer de nombreux dégâts aux secteurs avoisinants et notamment dans les zones de production des coquillages surtout si les espèces introduites sont constituées de phytoplancton toxique. Au terme de 4 années de suivi de la qualité phytoplanctonique des milieux portuaires du golfe de Gabès, nous avons pu inventorier certaines espèces toxiques pour la plupart nouvelles pour la flore phytoplanctonique du golfe à savoir l’Alexandrium margalefi Balech, l’A. fundyense Balech, l’A. insuetum Balech, l’A. ostenfeldii Balech et tangen, le Gymnodinium catenaum Graham et le Karenia papilionacea Haywood et Steidinger. Dans cette étude nous avons essayé de suivre l’évolution de ces espèces, du milieu portuaire vers les zones avoisinantes de production des coquillages. La nécessité d’instaurer un programme d’étude et de surveillance de ces transferts apparaît donc imminente.
    Description: أثبتت عديد الدراسات أن البواخر و مياه "بلاست" يمكن أن تتسبب في نقل وانتشار عدة كائنات جديدة من محيط إلى آخر. الطحالب المهجرية هي أحسن صورة لهذا الانتقال إلا أنها يمكن أن تتسبب في عدة إشكاليات بيئية أو حتى صحية و بالتالي اقتصادية لم تستطيع أن تفرزه من سموم. لمتابعة مدى انتشار و تأقلم الطحالب المهجرية السامة وغزوها لمناطق إنتاج القوقعيات في خليج قابس قمنا بمتابعة مياه المواني و دراسة هذه الكائنات بالجهة لمدة تقارب 4 سنوات وحددنا النوعيات السامة و كيفية تنقلها من موقع إلى آخر.
    Description: There is a strong evidence that harbours submitted to an intense maritime traffic receive ballast waters of ship possibly coming from various oceanic regions and parts of the world. The transfer and the invasion of several harmful species via ballast waters tipping and ship fouling have been amply summoned these last times. These introductions can cause many damages to the neighbouring sectors and particularly in zones of shellfish production mainly if the introduced species are constituted of harmful phytoplankton. At the end of a 4 years survey for phytoplankton quality of harbours surrounding the Gabes gulf, some toxic species were inventoried, some of them being new ones in the context of the Gulf phytoplankton flora such as Alexandrium margalefi, A. fundyense, A. insuetum, A. ostenfeldii, Gymnodinium catenaum and Karenia papilionacea. In this survey we tried to follow the evolution of these species, from the harbours areas toward bordering shellfish production areas. There is an urgent need to set up a monitoring program for these transfers .
    Description: Published
    Description: Alexandrium insuetum, Alexandrium ostenfeldii, Alexandrium undyense, Gymnodinium catenaum, Karenia papilionacea
    Keywords: Ballast ; Ecology ; Ecosystems ; Eutrophication ; Phytoplankton ; Pollution monitoring ; Toxicity
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 2
    Publication Date: 2021-05-19
    Description: Notas sobre la ecología de los lagartos de la isla Malpelo, Colombia. Observaciones de dos de las especies endémicas de lagartos de la isla Malpelo ofrecen características poco conocidas de su historia natural, ecología y estado poblacional. Anolis agassizi, el lagarto más abundante y ampliamente distribuido, se alimenta principalmente de insectos y excretas de aves marinas. Duerme sobre rocas grandes, en las paredes de los cerros o sobre estructuras construidas por el hombre y, aunque no defiende sitios de percha como la mayoría de Anolis, muestra predilección por sitios elevados en donde, entre otras actividades, realiza sus cópulas. Diploglossus millepunctatus, el lagarto de mayor tamaño corporal y menor abundancia, es un depredador-oportunista y carroñero que mantiene una relación inusual con el cangrejo terrestre de la Isla (Johngarthia malpilensis), al cual no solo depreda activamente, sino con el que también compite por alimentos. El comportamiento, mayor densidad, tamaño corporal y peso de los individuos de D. millepunctatus cercanos a las cabañas, sugieren que estos lagartos se han condicionado a la presencia de los humanos, al consumir periódicamente las sobras de sus comidas.
    Description: Observations of two of the endemic species of lizards of Malpelo Island provide new information on their natural history, ecology, and population size. Anolis agassizi, the most abundant and broadly distributed lizard, feeds mainly on insects and excrements of marine birds. It sleeps on large rocks, surfaces on hills or on man-made structures and, although it does not defend perch sites like most Anolis do, it does show preferences for high perches where, among other activities, it carries out copulation. Diploglossus millepunctatus, the largest and least abundant lizard, is an opportunistic-predator and scavenger that has a remarkable relationship with the land crab of the island (Johngarthia malpilensis) which it not only eats, but also competes with it for food. Behavior, higher density, larger body size and weight of individual D. millepunctatus living close to cabins suggest that these lizards accommodate to the presence of people by feeding on left-over food.
    Description: INVEMAR
    Description: Published
    Description: Anolis agassizi; Diploglossus millepunctatus; General behavior; Population status
    Keywords: Ecology
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 3
    Publication Date: 2021-05-19
    Description: La présente étude a porté sur une anomalie morphologique observée chez la palourde européenne Ruditapes decussatus collectée dans le lac nord de Tunis et des perturbations coquillières relevées chez la datte de mer Lithophaga lithophaga prélevée dans la baie de Bizerte. L’examen de la partie molle et de la coquille de ces deux espèces de bivalves a révélé une malformation chez la palourde européenne qui consiste en la différenciation de deux siphons inhalant et exhalant surnuméraires prenant naissance des deux siphons habituels, complètement séparés, inhalant et exhalant. Les siphons en forme de Y possèdent ainsi 4 ouvertures fonctionnelles au lieu de 2. Chez la datte de mer Lithophaga lithophaga, nous avons relevé la présence de perturbations coquillières qui touchent la valve du côté externe et interne. Nous avons mis en évidence la présence d’annélides perforateurs et de sipunculiens vivant à l’intérieur de galeries intravalvaires creusées vraisemblablement par ces invertébrés. La fine épaisseur de la coquille pourvue de galeries entraine des malformations morphologiques coquillières observées chez ce bivalve lithophage.
    Description: تبرز هذه الدراسة تشوهات لاحظناها في لحم القفالة Ruditapes decussatus التي تم التقاطها في بحيرة تونس الشمالية كما تسجل بعض الاضطرابات التي تخص قوقعة بلح البحر Lithophaga lithophaga المتأتية من شرم بنزرت. فبالنسبة للقفالة، لاحظنا ظهور مثاعب إضافية استنشاقية واستنثارية ثانية تبرز من المثاعب الأصلية المنفصلة حيث يبدو كل مثعب منهما على شكل «Y » بفتحتين في مؤخرتهما الخلفيتين. أما بالنسبة لبلح البحر، فقد لوحظت اضطرابات على مستوى قشرة قوقعية بلح البحر من داخله و خارجه على حد سواء، وهذه الإضطرابات ناتجة عن وجود كائنات بحرية من الافقاريات مثل ديدان الفول السوداني وديدان حلقية التي تسكن في أنفاق محفورة داخل قشرة القوقعية. إن شفافية سمك قوقعة بلح البحر يؤدي، عند وجود كائنات حية تعيش فيها إلى إحداث تشوهات في الشكل الداخلي والخارجي لقوقعية بلح البحر.
    Description: The present study concerned a morphological abnormality observed at the European clam Ruditapes decussatus collected in the north lake of Tunis and the shell disturbances raised to Lithophaga lithophaga taken in the bay of Bizerta. The examination of the soft part and the shell of these two sorts of bivalves revealed a deformation at the European clam who consists of the differentiation of two siphons inhaling and exhaling originating supernumeraries both usual siphons, siphons in the form of Y so possesses 4 functional openings instead of 2. To the sea date Lithophaga lithophaga, we raised the presence of shell disturbances which get the valve of the external and internal side. We put in evidence the presence of perforating annelids and sipunculians living inside intravalves galleries dug credibly by these invertebrates. The soft thickness of the shell provided with galleries entails morphological shell deformations and fragility observed to this lithophagous bivalve.
    Description: Published
    Keywords: Lithophaga lithophaga ; Ruditapes decussatus ; Abnormalities ; Animal morphology ; Ecology ; Shellfish ; Shells
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 4
    Publication Date: 2021-05-19
    Description: التطورات السريعة للتأريخ العرقي للإسفنج ، كذاك الأعمال الحديثة التي أحدثت في البلاد التونسية في علم التصنيف و علم البيئة لهذه المجموعة قد شجعتنا لإعادة النظر في التسميات. هذا التجديد مكننا أيضا اعتبار الإضافات و التسجيلات الأخيرة.
    Description: Les progrès rapides de la phylogénie des éponges en général et celle des démoponges en particulier, ainsi que les travaux récents entamés en Tunisie sur la taxonomie et l’écologie de ce groupe, nous ont encouragé à revoir leur nomenclature. Cette mise a jour nous a aussi permis de tenir compte des derniers ajouts et signalisations en Tunisie.
    Description: Fast progress of the phylogeny of sponges in general and that of the demoponges in particular, as well as recent works on the taxonomy and the ecology of this group in Tunisia, encouraged us to re-examine their nomenclature. This update also allowed us to take account of the last additions and indications in Tunisia.
    Description: Published
    Keywords: Porifera ; Taxonomy ; Terminology ; Ecology ; Phylogeny ; Sponges ; Ecology ; Phylogeny ; Sponges ; Taxonomy ; Terminology
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 5
    Publication Date: 2021-05-19
    Description: L’étude des résistances vis-à-vis de différentes substances antibiotiques pour des espèces bactériennes (aérobies et anaérobies) isolées chez Mytilus galloprovincialis a été réalisée par la méthode standard de l’antibiogramme. Ainsi, 50 souches bactériennes aérobies et 20 souches anaérobies appartenant à plus de 25 espèces différentes ont été isolées et testées. Les résultats obtenus montrent des profils à plusieurs résistances vis-à-vis des différentes familles d’antibiotiques testés. Les résultats obtenus révèlent des profils à 12 résistances différentes notamment chez l’espèce anaérobie (Propioni acnes). Aussi, chez l’espèce aérobie pré dominante ( Aeromonas hydrophila) nous avons mis en évidence au moins 6 antibiotypes différents. Ces résultats montrent la prépondérance de bactéries multirésistantes aux antibiotiques hébergeant dans la moule Mytilus galloprovincialis prélevée d’un milieu naturel (la lagune de Bizerte).
    Description: The sensitivity of various aerobic and anaerobic bacterial species isolated from Mytilus galloprovincialis to different types of antibiotics. Thus, sensitivity of 50 aerobic and 20 anaerobic species was tested to 15 antibiotics including (betalactams, aminosids, cephalo porins, phenicols, cyclins, macrolids, nitrofurans, sulfamids, rifamycins). According to results obtained, all strains tested demonstrate resistances profiles to 3 to 12 antibiotics tested. Multi resistant profiles to 12 different antibiotics were detected for the anaerobic species (Propioni acnes). For the main aerobic species isolated, Aeromonas hydrophila we described more than 6 different antibiotypes. According to these results, it seems that the multi resistant antibiotic bacteria were well spread in Mytilus galloprovincialis brought from natural Tunisian lagoon ecosystems (Lagoon of Bizerta)..
    Description: قمنا بدراسة مقاومة مجموعات من أنواع البكتيريات الهوائية واللاهوائية تم عزلها من محار)Mytilus galloprovincialis(، للمضادات الحيوية من مختلف الأصناف. ولقد تم عزل ودراسة 70 من مختلف الأجذال البكتيرية والتي تم تعريفها بالطرق البيوكيميائية. وقد أثبتت النتائج المتحصل عليها وجود رسوم طيفية ذات مقاومات متعددة لـ 12 مضاد حيوي لدى البكتيريا اللاهوائية من نوعPropioni acnes. كما قمنا بعزل مكثف للبكتيريا من نوع Aeromonas hydrophila، وثبت لدى هذا النوع من البكتيريا وجود أكثر من ستة رسوم طيفية مختلفة. وتبين هذه النتائج كثافة تواجد البكتيريات متعددة المقاومة لدى المحارMytilus galloprovincialis المتأتي من بحيرة بنزرت، وذلك يشمل كل أنواع البكتيريا المعزولة (أكثر من 25 أصناف مختلفة).
    Description: Published
    Keywords: Bacteria ; Mytilus galloprovincialis ; Antibiotics ; Bacterial diseases ; Control resistance ; Ecology ; Eutrophication ; Indicator species ; Microbiological analysis
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 6
    Publication Date: 2022-05-25
    Description: © The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 2 (2012): 553, doi:10.1038/srep00553.
    Description: Sea surface temperature imagery, satellite altimetry, and a surface drifter track reveal an unusual tilt in the Gulf Stream path that brought the Gulf Stream to 39.9°N near the Middle Atlantic Bight shelfbreak—200 km north of its mean position—in October 2011, while a large meander brought Gulf Stream water within 12 km of the shelfbreak in December 2011. Near-bottom temperature measurements from lobster traps on the outer continental shelf south of New England show distinct warming events (temperature increases exceeding 6°C) in November and December 2011. Moored profiler measurements over the continental slope show high salinities and temperatures, suggesting that the warm water on the continental shelf originated in the Gulf Stream. The combination of unusual water properties over the shelf and slope in late fall and the subsequent mild winter may affect seasonal stratification and habitat selection for marine life over the continental shelf in 2012.
    Description: Profiler data were made available by the Ocean Observatory Initiative (OOI) during the construction phase of the project. The OOI is funded by the National Science Foundation and managed by the Consortium for Ocean Leadership. Drifter data were provided by Tim Shaw and David Calhoun at Cape Fear Community College.GGGwas supported by NSFGrant OCE-1129125. RET was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Cooperative Institute for the North Atlantic Region. MA was supported by the Penzance Endowed Fund in Support of Assistant Scientists.
    Keywords: Ecology ; Climate change ; Atmospheric science ; Oceanography
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
    Publication Date: 2022-05-25
    Description: Author Posting. © The Natural History Museum, 2012. This article is posted here by permission of Taylor & Francis for reuse for non-commercial purposes only. The definitive version was published in Systematics and Biodiversity 10 (2012): 1-20, doi:10.1080/14772000.2012.665095.
    Description: The time is ripe for a comprehensive mission to explore and document Earth's species. This calls for a campaign to educate and inspire the next generation of professional and citizen species explorers, investments in cyber-infrastructure and collections to meet the unique needs of the producers and consumers of taxonomic information, and the formation and coordination of a multi-institutional, international, transdisciplinary community of researchers, scholars and engineers with the shared objective of creating a comprehensive inventory of species and detailed map of the biosphere. We conclude that an ambitious goal to describe 10 million species in less than 50 years is attainable based on the strength of 250 years of progress, worldwide collections, existing experts, technological innovation and collaborative teamwork. Existing digitization projects are overcoming obstacles of the past, facilitating collaboration and mobilizing literature, data, images and specimens through cyber technologies. Charting the biosphere is enormously complex, yet necessary expertise can be found through partnerships with engineers, information scientists, sociologists, ecologists, climate scientists, conservation biologists, industrial project managers and taxon specialists, from agrostologists to zoophytologists. Benefits to society of the proposed mission would be profound, immediate and enduring, from detection of early responses of flora and fauna to climate change to opening access to evolutionary designs for solutions to countless practical problems. The impacts on the biodiversity, environmental and evolutionary sciences would be transformative, from ecosystem models calibrated in detail to comprehensive understanding of the origin and evolution of life over its 3.8 billion year history. The resultant cyber-enabled taxonomy, or cybertaxonomy, would open access to biodiversity data to developing nations, assure access to reliable data about species, and change how scientists and citizens alike access, use and think about biological diversity information.
    Description: Funds for the ‘Sustain What?’ workshop were provided by Arizona State University (Office of the President, International Institute for Species Exploration and Global Institute of Sustainability) and a grant from the US National Science Foundation (DEB-1102500 to QDW). Further support was provided by the College of Liberal Arts and Sciences, Arizona State University and NSF (DEB-0316614 to SK).
    Keywords: Biodiversity ; Bioinformatics ; Biomimicry ; Biosphere ; Conservation ; Cyberinfrastructure ; Ecology ; Evolution ; International collaboration ; Organization of science ; Origins ; Species ; Sustainability ; Systematics ; Taxonomy ; Team work
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-05-25
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1989
    Description: This work comprises three detailed studies of ontogeny and ecology. In the first chapter, four living species of the ostracode genus Cyprideis were studied both morphologically and ecologically to determine whether differences in age at maturity are correlated with heterochrony as expected; accelerated maturity should yield generalized morphology and small size, while delayed maturity should produce specialized morphology and large size. Two of the four species show the expected pattern, the other two do not. Cyprideis does not support the generalization that life-history evolution causes heterochrony, and casts doubt on the inference of life-history evolution from heterochrony where the data are drawn exclusively from extinct forms. In the second chapter, populations of Globorotalia menardii and G. tumida were subjected to careful morphological analysis; the stable-isotopic composition of the growth stages revealed that both species inhabit the upper fifty meters of the ocean, descending to deeper water (75-l00m) for the emplacement of an enveloping calcite crust. The third chapter shows a simple relationship between proloculus size and rate of chamber expansion in the polar planktonic foraminifer Neogloboquadrina pachyderma. The consequences for morphology of variations in ontogeny can be used to suggest ways of selecting specimens that minimize ontogenetic variations in shell chemistry.
    Keywords: Ecology ; Paleontology ; Ontogeny
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 9
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    Nature Publishing Group (NPG)
    Publication Date: 2012-11-29
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2012 Nov 22;491(7425):496.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23189323" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aquatic Organisms/drug effects ; Ecology ; *Environmental Restoration and Remediation/economics/legislation & ; jurisprudence/trends ; Ethinyl Estradiol/adverse effects/analysis ; Fishes/abnormalities ; Great Britain ; International Cooperation ; *Water Purification/economics/legislation & jurisprudence ; *Water Supply/economics/legislation & jurisprudence
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2012-01-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Florens, F B Vincent -- England -- Nature. 2012 Jan 4;481(7379):29. doi: 10.1038/481029b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22222742" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biodiversity ; Conservation of Natural Resources/*legislation & jurisprudence ; Ecology ; Environmental Policy/*legislation & jurisprudence ; Mauritius
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 11
    Publication Date: 2012-06-09
    Description: Evidence is mounting that extinctions are altering key processes important to the productivity and sustainability of Earth's ecosystems. Further species loss will accelerate change in ecosystem processes, but it is unclear how these effects compare to the direct effects of other forms of environmental change that are both driving diversity loss and altering ecosystem function. Here we use a suite of meta-analyses of published data to show that the effects of species loss on productivity and decomposition--two processes important in all ecosystems--are of comparable magnitude to the effects of many other global environmental changes. In experiments, intermediate levels of species loss (21-40%) reduced plant production by 5-10%, comparable to previously documented effects of ultraviolet radiation and climate warming. Higher levels of extinction (41-60%) had effects rivalling those of ozone, acidification, elevated CO(2) and nutrient pollution. At intermediate levels, species loss generally had equal or greater effects on decomposition than did elevated CO(2) and nitrogen addition. The identity of species lost also had a large effect on changes in productivity and decomposition, generating a wide range of plausible outcomes for extinction. Despite the need for more studies on interactive effects of diversity loss and environmental changes, our analyses clearly show that the ecosystem consequences of local species loss are as quantitatively significant as the direct effects of several global change stressors that have mobilized major international concern and remediation efforts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hooper, David U -- Adair, E Carol -- Cardinale, Bradley J -- Byrnes, Jarrett E K -- Hungate, Bruce A -- Matulich, Kristin L -- Gonzalez, Andrew -- Duffy, J Emmett -- Gamfeldt, Lars -- O'Connor, Mary I -- England -- Nature. 2012 May 2;486(7401):105-8. doi: 10.1038/nature11118.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Western Washington University, Bellingham, Washington 98225-9160, USA. hooper@biol.wwu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22678289" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biodiversity ; Ecology ; *Ecosystem ; *Extinction, Biological ; Models, Biological
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 12
    Publication Date: 2012-10-27
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tollefson, Jeff -- England -- Nature. 2012 Oct 25;490(7421):458-9. doi: 10.1038/490458a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23099379" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aquatic Organisms/metabolism ; Canada ; Carbon Dioxide/metabolism ; *Carbon Sequestration ; Ecology ; Environmental Policy/*legislation & jurisprudence ; Oceans and Seas ; Phytoplankton/growth & development/metabolism ; Politics ; Salmon/*growth & development ; Seawater/*chemistry ; Uncertainty
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 13
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    Nature Publishing Group (NPG)
    Publication Date: 2012-04-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Qiu, Jane -- England -- Nature. 2012 Apr 2;484(7392):19. doi: 10.1038/484019a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22481333" target="_blank"〉PubMed〈/a〉
    Keywords: *Altitude ; Ecology ; Global Warming/*statistics & numerical data ; *Ice Cover ; *Research/trends ; Tibet ; Water Supply/*analysis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 14
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    Nature Publishing Group (NPG)
    Publication Date: 2012-02-03
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schrope, Mark -- England -- Nature. 2012 Feb 1;482(7383):20-1. doi: 10.1038/482020a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22297950" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aquatic Organisms/*growth & development/isolation & purification ; Cnidaria/*growth & development ; Ecology ; Internationality ; Marine Biology ; Population Growth
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 15
    Publication Date: 2012-06-23
    Description: Complex networks of interactions are ubiquitous and are particularly important in ecological communities, in which large numbers of species exhibit negative (for example, competition or predation) and positive (for example, mutualism) interactions with one another. Nestedness in mutualistic ecological networks is the tendency for ecological specialists to interact with a subset of species that also interact with more generalist species. Recent mathematical and computational analysis has suggested that such nestedness increases species richness. By examining previous results and applying computational approaches to 59 empirical data sets representing mutualistic plant-pollinator networks, we show that this statement is incorrect. A simpler metric-the number of mutualistic partners a species has-is a much better predictor of individual species survival and hence, community persistence. Nestedness is, at best, a secondary covariate rather than a causative factor for biodiversity in mutualistic communities. Analysis of complex networks should be accompanied by analysis of simpler, underpinning mechanisms that drive multiple higher-order network properties.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉James, Alex -- Pitchford, Jonathan W -- Plank, Michael J -- England -- Nature. 2012 Jul 12;487(7406):227-30. doi: 10.1038/nature11214.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biomathematics Research Centre, University of Canterbury, Private Bag 4800, Christchurch 8040, New Zealand. alex.james@canterbury.ac.nz〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722863" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biodiversity ; Ecology ; *Ecosystem ; *Models, Theoretical
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 16
    Publication Date: 2012-04-27
    Description: Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts. Organic farming-a system aimed at producing food with minimal harm to ecosystems, animals or humans-is often proposed as a solution. However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak-acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions-that is, with good management practices, particular crop types and growing conditions-organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Seufert, Verena -- Ramankutty, Navin -- Foley, Jonathan A -- England -- Nature. 2012 May 10;485(7397):229-32. doi: 10.1038/nature11069.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geography and Global Environmental and Climate Change Center, McGill University, Montreal, Quebec H2T 3A3, Canada. verena.seufert@mail.mcgill.ca〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22535250" target="_blank"〉PubMed〈/a〉
    Keywords: Agricultural Irrigation ; Agriculture/*methods ; Animals ; *Biomass ; Conservation of Natural Resources/*methods ; Crops, Agricultural/classification/growth & development ; Developed Countries ; Developing Countries ; Ecology ; Ecosystem ; Food Supply/*statistics & numerical data ; Food, Organic/supply & distribution ; Forestry ; Humans ; Hydrogen-Ion Concentration ; Organic Agriculture/*methods ; Population Growth ; Soil/analysis/chemistry ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 17
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    Unknown
    Nature Publishing Group (NPG)
    Publication Date: 2012-03-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2012 Mar 7;483(7388):123-4. doi: 10.1038/483123b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22398516" target="_blank"〉PubMed〈/a〉
    Keywords: Ecology ; Great Britain ; History, 20th Century ; Internationality ; National Socialism/history ; Physics/history ; *Politics ; Religion and Science ; *Science
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 18
    Publication Date: 2012-06-08
    Description: The human-microbial ecosystem plays a variety of important roles in human health and disease. Each person can be viewed as an island-like "patch" of habitat occupied by microbial assemblages formed by the fundamental processes of community ecology: dispersal, local diversification, environmental selection, and ecological drift. Community assembly theory, and metacommunity theory in particular, provides a framework for understanding the ecological dynamics of the human microbiome, such as compositional variability within and between hosts. We explore three core scenarios of human microbiome assembly: development in infants, representing assembly in previously unoccupied habitats; recovery from antibiotics, representing assembly after disturbance; and invasion by pathogens, representing assembly in the context of invasive species. Judicious application of ecological theory may lead to improved strategies for restoring and maintaining the microbiota and the crucial health-associated ecosystem services that it provides.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208626/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208626/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Costello, Elizabeth K -- Stagaman, Keaton -- Dethlefsen, Les -- Bohannan, Brendan J M -- Relman, David A -- DP1 OD000964/OD/NIH HHS/ -- DP1OD000964/OD/NIH HHS/ -- R01 GM095385/GM/NIGMS NIH HHS/ -- R01 OD011116/OD/NIH HHS/ -- R01GM095385/GM/NIGMS NIH HHS/ -- T32 GM007413/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2012 Jun 8;336(6086):1255-62. doi: 10.1126/science.1224203. Epub 2012 Jun 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22674335" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Anti-Bacterial Agents/pharmacology/*therapeutic use ; Bacterial Infections/*microbiology ; Biodiversity ; Ecology ; *Ecosystem ; Gastrointestinal Tract/*microbiology ; *Host-Pathogen Interactions ; Humans ; Infant, Newborn ; *Metagenome ; Selection, Genetic ; Symbiosis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 19
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Aerodynamics
    Type: E-664455 , NASA Advisory Council Aeronautics Committee Meeting; Oct 25, 2012 - Oct 26, 2012; Cleveland, OH; United States
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  • 20
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    Unknown
    In:  CASI
    Publication Date: 2019-07-13
    Description: Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217740 , E-18485 , 15th International Conference on Fluid Flow Technologies (CMFF''12); Sep 04, 2012 - Sep 07, 2012; Budapest; Hungary
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  • 21
    Publication Date: 2019-07-13
    Description: A simulation framework based on the Memory-Mapped-Files technique was created to operate multiple numerical processes in locked time-steps and send I/O data synchronously across to one-another to simulate system-dynamics. This simulation scheme is currently used to study the complex interactions between inlet flow-dynamics, variable-geometry actuation mechanisms, and flow-controls in the transition from the supersonic to hypersonic conditions and vice-versa. A study of Mode-Transition Control for a high-speed inlet wind-tunnel model with this MMF-based framework is presented to illustrate this scheme and demonstrate its usefulness in simulating supersonic and hypersonic inlet dynamics and controls or other types of complex systems.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-4144 , E-18463 , 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference; Jul 30, 2012 - Aug 01, 2012; Atlanta, GA; United States
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  • 22
    Publication Date: 2019-07-13
    Description: An overview of the recent facility modifications to NASA s Transonic Turbine Blade Cascade Facility and aerodynamic measurements on the VSPT incidence-tolerant blade are presented. This work supports the development of variable-speed power turbine (VSPT) speed-change technology for the NASA Large Civil Tilt Rotor (LCTR) vehicle. In order to maintain acceptable main rotor propulsive efficiency, the VSPT operates over a nearly 50% speed range from takeoff to altitude cruise. This results in 50 or more variations in VSPT blade incidence angles. The Transonic Turbine Blade Cascade Facility has the ability to operate over a wide range of Reynolds numbers and Mach numbers, but had to be modified in order to accommodate the negative incidence angle variation required by the LCTR VSPT operation. Details of the modifications are described. An incidence-tolerant blade was developed under an RTPAS study contract and tested in the cascade to look at the effects of large incidence angle and Reynolds number variations. Recent test results are presented which include midspan exit total pressure and flow angle measurements obtained at three inlet angles representing the cruise, take-off, and maximum incidence flight mission points. For each inlet angle, data were obtained at five flow conditions with exit Reynolds numbers varying from 2.12 106 to 2.12 105 and two isentropic exit Mach numbers of 0.72 and 0.35. Three-dimensional flowfield measurements were also acquired at the cruise and take-off points. The flowfield measurements were acquired using a five-hole and three-hole pneumatic probe located in a survey plane 8.6% axial chord downstream of the blade trailing edge plane and covering three blade passages. Blade and endwall static pressure distributions were also acquired for each flow condition.
    Keywords: Aerodynamics
    Type: E-18470 , 2012 Fundamental Aeronautics Programs (FAP) Technical Conference; Mar 13, 2012 - Mar 15, 2012; Cleveland, OH; United States
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  • 23
    Publication Date: 2019-07-13
    Description: An open rotor experiment was conducted at cruise Mach numbers and the unsteady pressure in the nearfield was measured. The system included extensive performance measurements, which can help provide insight into the noise generating mechanisms in the absence of flow measurements. A set of data acquired at a constant blade pitch angle but various rotor speeds was examined. The tone levels generated by the front and rear rotor were found to be nearly equal when the thrust was evenly balanced between rotors.
    Keywords: Aerodynamics
    Type: E-18347-1 , 18th AIAA/CEAS Aeroacoustics Conference; Jun 04, 2012 - Jun 06, 2012; Colorado Spring, CO; United States|33rd AIAA Aeroacoustics Conference; Jun 04, 2012 - Jun 06, 2012; Colorado Spring, CO; United States
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  • 24
    Publication Date: 2019-07-13
    Description: A procedure to compute flutter boundaries of rotating blades is presented; a) Navier-Stokes equations. b) Frequency domain method compatible with industry practice. Procedure is initially validated: a) Unsteady loads with flapping wing experiment. b) Flutter boundary with fixed wing experiment. Large scale flutter computation is demonstrated for rotating blade: a) Single job submission script. b) Flutter boundary in 24 hour wall clock time with 100 cores. c) Linearly scalable with number of cores. Tested with 1000 cores that produced data in 25 hrs for 10 flutter boundaries. Further wall-clock speed-up is possible by performing parallel computations within each case.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN6026 , AIAA Multidisciplinary Analysis and Optimization Conference; Sep 17, 2012 - Sep 19, 2012; Indanapolis, IN; United States
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  • 25
    Publication Date: 2019-07-13
    Description: This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy faculties. The geometry corresponded to "Pak B" LPT airfoil. The test section simulated LPT flow in a passage. Three experimental studies were performed: (a) Boundary layer measurements for ten baseline cases under high and low freestream turbulence conditions at five Reynolds numbers of 25,000, 50,000, 100,000, 200,000, and 300,000, based on passage exit velocity and suction surface wetted length; (b) Passive flow control studies with three thicknesses of two-dimensional bars, and two heights of three-dimensional circular cylinders with different spanwise separations, at same flow conditions as the 10 baseline cases; (c) Active flow control with oscillating synthetic (zero net mass flow) vortex generator jets, for one case with low freestream turbulence and a low Reynolds number of 25,000. The Passive flow control was successful at controlling the separation problem at low Reynolds numbers, with varying degrees of success from case to case and varying levels of impact at higher Reynolds numbers. The active flow control successfully eliminated the large separation problem for the low Reynolds number case. Very detailed data was acquired using hot-wire anemometry, including single and two velocity components, integral boundary layer quantities, turbulence statistics and spectra, turbulent shear stresses and their spectra, and intermittency, documenting transition, separation and reattachment. Models were constructed to correlate the results. The report includes a summary of the work performed and reprints of the publications describing the various studies.This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy faculties. The geometry corresponded to "Pak B" LPT airfoil. The test section simulated LPT flow in a passage. Three experimental studies were performed: (a) Boundary layer measurements for ten baseline cases under high and low freestream turbulence conditions at five Reynolds numbers of 25,000, 50,000, 100,000, 200,000, and 300,000, based on passage exit velocity and suction surface wetted length; (b) Passive flow control studies with three thicknesses of two-dimensional bars, and two heights of three-dimensional circular cylinders with different spanwise separations, at same flow conditions as the 10 baseline cases; (c) Active flow control with oscillating synthetic (zero net mass flow) vortex generator jets, for one case with low freestream turbulence and a low Reynolds number of 25,000. The Passive flow control was successful at controlling the separation problem at low Reynolds numbers, with varying degrees of success from case to case and varying levels of impact at higher Reynolds numbers. The active flow control successfully eliminated the large separation problem for the low Reynolds number case. Very detailed data was acquired using hot-wire anemometry, including single and two velocity components, integral boundary layer quantities, turbulence statistics and spectra, turbulent shear stresses and their spectra, and intermittency, documenting transition, separation and reattachment. Models were constructed to correlate the results. The report includes a summary of the work performed and reprints of the publications describing the various studies. The folders in this supplement contain processed data in ASCII format. Streamwise pressure profiles and velocity profiles are included. The velocity profiles were acquired using single sensor and cross sensor hot-wire probes which were traversed from the wall to the freestream at various streamwise locations. In some of the flow control cases (3D Trips and Jets) profiles were acquired at multiple spanwise locations.
    Keywords: Aerodynamics
    Type: NASA/CR-2012-217656/SUPPL , E-18233
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  • 26
    Publication Date: 2019-07-13
    Description: This presentation contains Wind-US results presented at the 1st Propulsion Aerodynamics Workshop. The The workshop was organized by the American Institute of Aeronautics and Astronautics, Air Breathing Propulsion Propulsion Systems Integration Technical Committee with the purpose of assessing the accuracy of computational computational fluid dynamics for air breathing propulsion applications. Attendees included representatives from representatives from government, industry, academia, and commercial software companies. Participants were were encouraged to explore and discuss all aspects of the simulation process including the effects of mesh type and mesh type and refinement, solver numerical schemes, and turbulence modeling. The first set of challenge cases involved computing the thrust and discharge coefficients for a series of convergent convergent nozzles for a range of nozzle pressure ratios between 1.4 and 7.0. These configurations included a included a reference axisymmetric nozzle as well as 15deg , 25deg , and 40deg conical nozzles. Participants were also asked also asked to examine the plume shock structure for two cases where the 25deg conical nozzle was bifurcated by a bifurcated by a solid plate. The final test case was a serpentine inlet diffuser with an outlet to inlet area ratio of 1.52 ratio of 1.52 and an offset of 1.34 times the inlet diameter. Boundary layer profiles, wall static pressure, and total and total pressure at downstream rake locations were examined.
    Keywords: Aerodynamics
    Type: E-18411 , AIAA 1st Propulsion Aerodynamics Workshop; Jul 29, 2012; Atlanta, GA; United States
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  • 27
    Publication Date: 2019-07-13
    Description: This paper summarizes data and findings from the first Aeroelastic Prediction Workshop (AePW) held in April, 2012. The workshop has been designed as a series of technical interchange meetings to assess the state of the art of computational methods for predicting unsteady flowfields and static and dynamic aeroelastic response. The goals are to provide an impartial forum to evaluate the effectiveness of existing computer codes and modeling techniques to simulate aeroelastic problems, and to identify computational and experimental areas needing additional research and development. For this initial workshop, three subject configurations have been chosen from existing wind tunnel data sets where there is pertinent experimental data available for comparison. Participant researchers analyzed one or more of the subject configurations and results from all of these computations were compared at the workshop. Keywords: Unsteady Aerodynamics, Aeroelasticity, Computational Fluid Dynamics, Transonic Flow, Separated Flow.
    Keywords: Aerodynamics
    Type: NF1676L-13995 , International Conference on Computational Fluid Dynamics; Jul 09, 2012 - Jul 13, 2012; Kohala Coast, HI; United States
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  • 28
    Publication Date: 2019-07-13
    Description: This paper reports the result of an analysis of wind tunnel data acquired in support of the Facility Analysis Verification & Operational Reliability (FAVOR) project. The analysis uses methods referred to collectively at Langley Research Center as the Modern Design of Experiments (MDOE). These methods quantify the total variance in a sample of wind tunnel data and partition it into explained and unexplained components. The unexplained component is further partitioned in random and systematic components. This analysis was performed on data acquired in similar wind tunnel tests executed in four different U.S. transonic facilities. The measurement environment of each facility was quantified and compared.
    Keywords: Aerodynamics
    Type: NF1676L-14983 , 28th AIAA Aerodynamic Measurement Technology, Ground Testing, and Flight Testing Conference; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 29
    Publication Date: 2019-07-13
    Description: Presenting an overview of the research DFRC is planning within the Subsonic Fixed Wing (SFW) Light Weight Airframes and Propulsion. Describ ing our TRL maturation and new research going forward using the X-56A as a validation testbed.
    Keywords: Aerodynamics
    Type: DFRC-E-DAA-TN4938 , Fundamental Aero Program Technical Conference; Mar 13, 2012 - Mar 15, 2012; Cleveland, OH; United States
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  • 30
    Publication Date: 2019-07-13
    Description: The rotor tips of axial turbines experience high heat flux and are the cause of aerodynamic losses due to tip clearance flows, and in the case of supersonic tips, shocks. As stage loadings increase, the flow in the tip gap approaches and exceeds sonic conditions. This introduces effects such as shock-boundary layer interactions and choked flow that are not observed for subsonic tip flows that have been studied extensively in literature. This work simulates the tip clearance flow for a flat tip, a diverging tip gap and several contoured tips to assess the possibility of minimizing tip heat flux while maintaining a constant massflow from the pressure side to the suction side of the rotor, through the tip clearance. The Computational Fluid Dynamics (CFD) code GlennHT was used for the simulations. Due to the strong favorable pressure gradients the simulations assumed laminar conditions in the tip gap. The nominal tip gap width to height ratio for this study is 6.0. The Reynolds number of the flow is 2.4 x 10(exp 5) based on nominal tip width and exit velocity. A wavy wall design was found to reduce heat flux by 5 percent but suffered from an additional 6 percent in aerodynamic loss coefficient. Conventional tip recesses are found to perform far worse than a flat tip due to severe shock heating. Overall, the baseline flat tip was the second best performer. A diverging converging tip gap with a hole was found to be the best choice. Average tip heat flux was reduced by 37 percent and aerodynamic losses were cut by over 6 percent.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217607 , GT2011-46390 , E-18188 , TURBO EXPO 2011; Jun 06, 2011 - Jun 10, 2011; Vancouver, BC; Canada
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  • 31
    Publication Date: 2019-07-13
    Description: The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217449 , AIAA Paper 2012-0823 , E-18179 , 50th Aerospace Sciences Meeting; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 32
    Publication Date: 2019-07-13
    Description: Despite significant advancements in computational fluid dynamics and their coupling with computational structural dynamics (= CSD, or comprehensive codes) for rotorcraft applications, CSD codes with their engineering level of modeling the rotor blade dynamics, the unsteady sectional aerodynamics and the vortical wake are still the workhorse for the majority of applications. This is especially true when a large number of parameter variations is to be performed and their impact on performance, structural loads, vibration and noise is to be judged in an approximate yet reliable and as accurate as possible manner. In this paper, the capabilities of such codes are evaluated using the HART II Inter- national Workshop data base, focusing on a typical descent operating condition which includes strong blade-vortex interactions. Three cases are of interest: the baseline case and two cases with 3/rev higher harmonic blade root pitch control (HHC) with different control phases employed. One setting is for minimum blade-vortex interaction noise radiation and the other one for minimum vibration generation. The challenge is to correctly predict the wake physics - especially for the cases with HHC - and all the dynamics, aerodynamics, modifications of the wake structure and the aero-acoustics coming with it. It is observed that the comprehensive codes used today have a surprisingly good predictive capability when they appropriately account for all of the physics involved. The minimum requirements to obtain these results are outlined.
    Keywords: Aerodynamics
    Type: NF1676L-13597 , American Helicopter Society 68th Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Forth Worth, TX; United States
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  • 33
    Publication Date: 2019-07-13
    Description: Supersonic travel is not allowed over populated areas due to the disturbance caused by the sonic boom. Research has been performed on sonic boom reduction and has included the contribution of the exhaust nozzle plume. Plume effect on sonic boom has progressed from the study of isolated nozzles to a study with four exhaust plumes integrated with a wing-body vehicle. This report provides a baseline analysis of the generic wing-body vehicle to demonstrate the effect of the nozzle exhaust on the near-field pressure profile. Reductions occurred in the peak-to-peak magnitude of the pressure profile for a swept wing-body vehicle. The exhaust plumes also had a favorable effect as the nozzles were moved outward along the wing-span.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217446 , E-18176 , AIAA Paper 2012-1033 , 50th Aerospace Science Conference; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 34
    Publication Date: 2019-07-13
    Description: An unsteady Reynolds-averaged Navier-Stokes solver for unstructured grids is used to simulate the flow over a UH-60A rotor. Traditionally, the computed pressure and shear stresses are integrated on the computational mesh at selected radial stations and compared to measured airloads. However, the corresponding integration of experimental data uses only the pressure contribution, and the set of integration points (pressure taps) is modest compared to the computational mesh resolution. This paper examines the difference between the traditional integration of computed airloads and an integration consistent with that used for the experimental data. In addition, a comparison of chordwise pressure distributions between computation and measurement is made. Examination of this unsteady pressure data provides new opportunities to understand differences between computation and flight measurement.
    Keywords: Aerodynamics
    Type: NF1676L-13528 , American Helicopter Society 68th Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Fort Worth, TX; United States
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  • 35
    Publication Date: 2019-07-13
    Description: Recent wind-tunnel tests at the NASA Langley Research Center National Transonic Facility utilized high-pressure bellows to route air to the model for evaluating aircraft circulation control. The introduction of these bellows within the Sidewall Model Support System significantly impacted the performance of the external sidewall mounted semi-span balance. As a result of this impact on the semi-span balance measurement performance, it became apparent that a new capability needed to be built into the National Transonic Facility s infrastructure to allow for performing pressure tare calibrations on the balance in order to properly characterize its performance under the influence of static bellows pressure tare loads and bellows thermal effects. The objective of this study was to design both mechanical calibration hardware and an experimental calibration design that can be employed at the facility in order to efficiently and precisely perform the necessary loadings in order to characterize the semi-span balance under the influence of multiple calibration factors (balance forces/moments and bellows pressure/temperature). Using statistical design of experiments, an experimental design was developed allowing for strategically characterizing the behavior of the semi-span balance for use in circulation control and propulsion-type flow control testing at the National Transonic Facility.
    Keywords: Aerodynamics
    Type: NF1676L-14440 , NF1676L-13863 , 28th Aerodynamic Meaurement Technology, Ground Testing and Flight Testing Conference; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States|8th International Symposium on Strain-Gauge Balances; May 07, 2012 - May 10, 2012; Lucerne; Switzerland
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  • 36
    Publication Date: 2019-07-13
    Description: Projection moir interferometry (PMI) was employed to measure blade deflections during a hover test of a generic model-scale rotor in the NASA Langley 14x22 subsonic wind tunnel s hover facility. PMI was one of several optical measurement techniques tasked to acquire deflection and flow visualization data for a rotor at several distinct heights above a ground plane. Two of the main objectives of this test were to demonstrate that multiple optical measurement techniques can be used simultaneously to acquire data and to identify and address deficiencies in the techniques. Several PMI-specific technical challenges needed to be addressed during the test and in post-processing of the data. These challenges included developing an efficient and accurate calibration method for an extremely large (65 inch) height range; automating the analysis of the large amount of data acquired during the test; and developing a method to determinate the absolute displacement of rotor blades without a required anchor point measurement. The results indicate that the use of a single-camera/single-projector approach for the large height range reduced the accuracy of the PMI system compared to PMI systems designed for smaller height ranges. The lack of the anchor point measurement (due to a technical issue with one of the other measurement techniques) limited the ability of the PMI system to correctly measure blade displacements to only one of the three rotor heights tested. The new calibration technique reduced the data required by 80 percent while new post-processing algorithms successfully automated the process of locating rotor blades in images, determining the blade quarter chord location, and calculating the blade root and blade tip heights above the ground plane.
    Keywords: Aerodynamics
    Type: NF1676L-13472 , 68th American Helicopter Society (AHS) Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Fort Worth, TX; United States
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  • 37
    Publication Date: 2019-07-13
    Description: A variable-speed power turbine concept is analyzed for rotordynamic feasibility in a Large Civil Tilt-Rotor (LCTR) class engine. Implementation of a variable-speed power turbine in a rotorcraft engine would enable high efficiency propulsion at the high forward velocities anticipated of large tilt-rotor vehicles. Therefore, rotordynamics is a critical issue for this engine concept. A preliminary feasibility study is presented herein to address this concern and identify if variable-speed is possible in a conceptual engine sized for the LCTR. The analysis considers critical speed placement in the operating speed envelope, stability analysis up to the maximum anticipated operating speed, and potential unbalance response amplitudes to determine that a variable-speed power turbine is likely to be challenging, but not impossible to achieve in a tilt-rotor propulsion engine.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217134 , E-17869 , E-17869-1 , 68th Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Fort Worth, TX; United States
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  • 38
    Publication Date: 2019-07-13
    Description: A summary of the computational aeroelastic analysis for the Semi-Span Super-Sonic Transport (S4T) wind-tunnel model is presented. A broad range of analysis techniques, including linear, nonlinear and Reduced Order Models (ROMs) were employed in support of a series of aeroelastic (AE) and aeroservoelastic (ASE) wind-tunnel tests conducted in the Transonic Dynamics Tunnel (TDT) at NASA Langley Research Center. This research was performed in support of the ASE element in the Supersonics Program, part of NASA's Fundamental Aeronautics Program. The analysis concentrated on open-loop flutter predictions, which were in good agreement with experimental results. This paper is one in a series that comprise a special S4T technical session, which summarizes the S4T project.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1556 , NF1676L-13333 , 13th AIAA Gossamer Systems Forum; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States|14th AIAA Non-Deterministic Approaches Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States|53rd Structures, Structural Dynamics, and Materials Conference (SDM); Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States|20th AIAA/ASME/AHS Adaptive Structures Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 39
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: Flow field survey results for three rectangular nozzles are presented for a low subsonic condition obtained primarily by hot-wire anemometry. The three nozzles have aspect ratios of 2:1, 4:1 and 8:1. A fourth case included has 2:1 aspect ratio with chevrons added to the long edges. Data on mean velocity, turbulent normal and shear stresses as well as streamwise vorticity are presented covering a streamwise distance up to sixteen equivalent diameters from the nozzle exit. These detailed flow properties, including initial boundary layer characteristics, are usually difficult to measure in high speed flows and the primary objective of the study is to aid ongoing and future computational and noise modeling efforts. This supplement contains data files, charts and source code.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217410/SUPPL , AIAA Paper 2012-0069 , E-18082 , 50th AIAA Aerospace Sciences Meeting; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 40
    Publication Date: 2019-07-13
    Description: The design-point and off-design performance of an embedded 1.5-stage portion of a variable-speed power turbine (VSPT) was assessed using Reynolds-Averaged Navier-Stokes (RANS) analyses with mixing-planes and sector-periodic, unsteady RANS analyses. The VSPT provides one means by which to effect the nearly 50 percent main-rotor speed change required for the NASA Large Civil Tilt-Rotor (LCTR) application. The change in VSPT shaft-speed during the LCTR mission results in blade-row incidence angle changes of as high as 55 . Negative incidence levels of this magnitude at takeoff operation give rise to a vortical flow structure in the pressure-side cove of a high-turn rotor that transports low-momentum flow toward the casing endwall. The intent of the effort was to assess the impact of unsteadiness of blade-row interaction on the time-mean flow and, specifically, to identify potential departure from the predicted trend of efficiency with shaft-speed change of meanline and 3-D RANS/mixing-plane analyses used for design.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217425 , AIAA Paper 2012-0937 , E-18113 , 50th Aerospace Science Conference; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 41
    Publication Date: 2019-07-13
    Description: This report provides an assessment of current turbulent flow calculation methods for hypersonic propulsion flowpaths, particularly the scramjet engine. Emphasis is placed on Reynolds-averaged Navier-Stokes (RANS) methods, but some discussion of newer meth- ods such as Large Eddy Simulation (LES) is also provided. The report is organized by considering technical issues throughout the scramjet-powered vehicle flowpath including laminar-to-turbulent boundary layer transition, shock wave / turbulent boundary layer interactions, scalar transport modeling (specifically the significance of turbulent Prandtl and Schmidt numbers) and compressible mixing. Unit problems are primarily used to conduct the assessment. In the combustor, results from calculations of a direct connect supersonic combustion experiment are also used to address the effects of turbulence model selection and in particular settings for the turbulent Prandtl and Schmidt numbers. It is concluded that RANS turbulence modeling shortfalls are still a major limitation to the accuracy of hypersonic propulsion simulations, whether considering individual components or an overall system. Newer methods such as LES-based techniques may be promising, but are not yet at a maturity to be used routinely by the hypersonic propulsion community. The need for fundamental experiments to provide data for turbulence model development and validation is discussed.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217277 , AIAA Paper 2011-5917 , E-18032 , 47th Joint Propulsion Conference and Exhibit; Jul 31, 2011 - Aug 03, 2011; San Diego, CA; United States
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  • 42
    Publication Date: 2019-07-13
    Description: Orthogonal harmonic multisine excitations were utilized in a wind tunnel test and in simulation of the SemiSpan Supersonic Transport model to assess aeroservoelastic characteristics. Fundamental issues associated with analyzing sinusoidal signals were examined, including spectral leakage, excitation truncation, and uncertainties on frequency response functions and mean-square coherence. Simulation allowed for evaluation of these issues relative to a truth model, while wind tunnel data introduced real-world implementation issues.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1404 , NF1676L-13303 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 43
    Publication Date: 2019-07-13
    Description: This paper describes a scalable structural model suitable for Hybrid Wing Body (HWB) centerbody analysis and optimization. The geometry of the centerbody and primary wing structure is based on a Vehicle Sketch Pad (VSP) surface model of the aircraft and a FLOPS compatible parameterization of the centerbody. Structural analysis, optimization, and weight calculation are based on a Nastran finite element model of the primary HWB structural components, featuring centerbody, mid section, and outboard wing. Different centerbody designs like single bay or multi-bay options are analyzed and weight calculations are compared to current FLOPS results. For proper structural sizing and weight estimation, internal pressure and maneuver flight loads are applied. Results are presented for aerodynamic loads, deformations, and centerbody weight.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1606 , NF1676L-13304 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 44
    Publication Date: 2019-07-13
    Description: A summary of computational and experimental aeroelastic (AE) and aeroservoelastic (ASE) results for the Semi-Span Super-Sonic Transport (S4T) wind-tunnel model is presented. A broad range of analyses and multiple AE and ASE wind-tunnel tests of the S4T wind-tunnel model have been performed in support of the ASE element in the Supersonics Program, part of the NASA Fundamental Aeronautics Program. This paper is intended to be an overview of multiple papers that comprise a special S4T technical session. Along those lines, a brief description of the design and hardware of the S4T wind-tunnel model will be presented. Computational results presented include linear and nonlinear aeroelastic analyses, and rapid aeroelastic analyses using CFD-based reduced-order models (ROMs). A brief survey of some of the experimental results from two open-loop and two closed-loop wind-tunnel tests performed at the NASA Langley Transonic Dynamics Tunnel (TDT) will be presented as well.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1552 , NF1676L-13307 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 45
    Publication Date: 2019-07-13
    Description: This paper focuses on some of the more challenging design processes and characterization tests of the Semi-Span Super-Sonic Transport (S4T)-Active Controls Testbed (ACT). The model was successfully tested in four entries in the National Aeronautics and Space Administration Langley Transonic Dynamics Tunnel to satisfy the goals and objectives of the Fundamental Aeronautics Program Supersonic Project Aero-Propulso-Servo-Elastic effort. Due to the complexity of the S4T-ACT, only a small sample of the technical challenges for designing and characterizing the model will be presented. Specifically, the challenges encountered in designing the model include scaling the Technology Concept Airplane to model scale, designing the model fuselage, aileron actuator, and engine pylons. Characterization tests included full model ground vibration tests, wing stiffness measurements, geometry measurements, proof load testing, and measurement of fuselage static and dynamic properties.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1553 , NF1676L-13306 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 46
    Publication Date: 2019-07-13
    Description: An important objective of the Semi-Span Super-Sonic Transport (S4T) wind tunnel model program was the demonstration of Flutter Suppression (FS), Gust Load Alleviation (GLA), and Ride Quality Enhancement (RQE). It was critical to evaluate the stability and robustness of these control laws analytically before testing them and experimentally while testing them to ensure safety of the model and the wind tunnel. MATLAB based software was applied to evaluate the performance of closed-loop systems in terms of stability and robustness. Existing software tools were extended to use analytical representations of the S4T and the control laws to analyze and evaluate the control laws prior to testing. Lessons were learned about the complex windtunnel model and experimental testing. The open-loop flutter boundary was determined from the closed-loop systems. A MATLAB/Simulink Simulation developed under the program is available for future work to improve the CPE process. This paper is one of a series of that comprise a special session, which summarizes the S4T wind-tunnel program.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1554 , NF1676L-13302 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 47
    Publication Date: 2019-07-13
    Description: Progress on a joint experimental and numerical study of laminar-to-turbulent transition induced by an isolated roughness element in a high-speed laminar boundary layer is reported in this paper. The numerical analysis suggests that transition is driven by the instability of high- and low-speed streaks embedded in the wake of the isolated roughness element. In addition, spatial stability analysis revealed that the wake flow supports multiple modes (even and odd) of convective instabilities that experience strong enough growth to cause transition. The experimental measurements, which included hot-wire and pitot-probe surveys, confirmed the existence of embedded high- and low-speed streaks in the roughness wake. Furthermore, the measurements indicate the presence of both even and odd modes of instability, although their relative magnitude depends on the specifics of the roughness geometry and flow conditions (e.g., the value of Re(sub kk) or k/delta. For the two test cases considered in the measurements (Re(sub kk) values of 462 and 319), the even mode and the odd mode were respectively dominant and appear to play a primary role in the transition process.
    Keywords: Aerodynamics
    Type: NF1676L-14423 , RTO AVT-200 RSM-030 Specialists'' Meeting on Hypersonic Laminar-Turbulent Transition; Apr 16, 2012 - Apr 19, 2012; San Diego, CA; United States
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  • 48
    Publication Date: 2019-07-13
    Description: Boundary-layer receptivity and stability of Mach 6 flow over smooth and rough 7 half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances are considered. The effects of two-dimensional isolated and distributed roughness on the receptivity and stability are also simulated. The results show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. An isolated two-dimensional roughness element of height h/delta =1/4 did not produce any difference in the receptivity or in the stability of the boundary layer. Distributed roughness elements produced a small decrease in the receptivity coefficient and also stabilized the boundary layer by small amounts.
    Keywords: Aerodynamics
    Type: NF1676L-14447 , RTO AVT-200 RSM-030 Specialists'' Meeting on Hypersonic Laminar-Turbulent Transition; Apr 16, 2012 - Apr 19, 2012; San Diego, CA; United States
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  • 49
    Publication Date: 2019-07-13
    Description: While PCB-132 sensors have proven useful for measuring second-mode instability waves in many hypersonic wind tunnels, they are currently limited by their calibration. Until now, the factory calibration has been all that was available, which is a single-point calibration at an amplitude three orders of magnitude higher than a second-mode wave. In addition, little information has been available about the frequency response or spatial resolution of the sensors, which is important for measuring high-frequency instability waves. These shortcomings make it difficult to compare measurements at different conditions and between different sensors. If accurate quantitative measurements could be performed, comparisons of the growth and breakdown of instability waves could be made in different facilities, possibly leading to a method of predicting the amplitude at which the waves break down into turbulence, improving transition prediction. A method for calibrating the sensors is proposed using a newly-built shock tube at Purdue University. This shock tube, essentially a half-scale version of the 6-Inch shock tube at the Graduate Aerospace Laboratories at Caltech, has been designed to attain a moderate vacuum in the driven section. Low driven pressures should allow the creation of very weak, yet still relatively thin shock waves. It is expected that static pressure rises within the range of second-mode amplitudes should be possible. The shock tube has been designed to create clean, planar shock waves with a laminar boundary layer to allow for accurate calibrations. Stronger shock waves can be used to identify the frequency response of the sensors out to hundreds of kilohertz.
    Keywords: Aerodynamics
    Type: NF1676L-13491 , RTO AVT-200 RSM-030 Specialists'' Meeting on Hypersonic Laminar-Turbulent Transition; Apr 16, 2012 - Apr 19, 2012; San Diego, CA; United States
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  • 50
    Publication Date: 2019-07-13
    Description: This paper provides an overview of ongoing efforts to develop, evaluate, and validate different tools for improved aerodynamic modeling and systems analysis of Hybrid Wing Body (HWB) aircraft configurations. Results are being presented for the evaluation of different aerodynamic tools including panel methods, enhanced panel methods with viscous drag prediction, and computational fluid dynamics. Emphasis is placed on proper prediction of aerodynamic loads for structural sizing as well as viscous drag prediction to develop drag polars for HWB conceptual design optimization. Data from transonic wind tunnel tests at the Arnold Engineering Development Center s 16-Foot Transonic Tunnel was used as a reference data set in order to evaluate the accuracy of the aerodynamic tools. Triangularized surface data and Vehicle Sketch Pad (VSP) models of an X-48B 2% scale wind tunnel model were used to generate input and model files for the different analysis tools. In support of ongoing HWB scaling studies within the NASA Environmentally Responsible Aviation (ERA) program, an improved finite element based structural analysis and weight estimation tool for HWB center bodies is currently under development. Aerodynamic results from these analyses are used to provide additional aerodynamic validation data.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-0249 , NF1676L-12880 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 51
    Publication Date: 2019-07-13
    Description: The fast-time wake transport and decay models require vertical profiles of crosswinds, potential temperature and the eddy dissipation rate as initial conditions. These inputs are normally obtained from various field sensors. In case of data-denied scenarios or operational use, these initial conditions can be provided by mesoscale model simulations. In this study, the vertical profiles of potential temperature from a mesoscale model were used as initial conditions for the fast-time wake models. The mesoscale model simulations were compared against available observations and the wake model predictions were compared with the Lidar measurements from three wake vortex field experiments.
    Keywords: Aerodynamics
    Type: AIAA 2013-0510 , NF1676L-14681 , 51st AIAA Aerospace Sciences Meeting; Jan 07, 2013 - Jan 10, 2013; Grapevine, TX; United States
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  • 52
    Publication Date: 2019-07-13
    Description: Separation can be seen in most aerodynamic flows, but accurate prediction of separated flows is still a challenging problem for computational fluid dynamics (CFD) tools. The behavior of several Reynolds Averaged Navier-Stokes (RANS) models in predicting the separated ow over a wall-mounted hump is studied. The strengths and weaknesses of the most popular RANS models (Spalart-Allmaras, k-epsilon, k-omega, k-omega-SST) are evaluated using the open source software OpenFOAM. The hump ow modeled in this work has been documented in the 2004 CFD Validation Workshop on Synthetic Jets and Turbulent Separation Control. Only the baseline case is treated; the slot flow control cases are not considered in this paper. Particular attention is given to predicting the size of the recirculation bubble, the position of the reattachment point, and the velocity profiles downstream of the hump.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN6770 , 44th AIAA Thermophysics Conference; Dec 19, 2012 - Dec 21, 2012; San Diego, CA; United States
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  • 53
    Publication Date: 2019-07-13
    Description: Time-dependent Navier-Stokes simulations have been carried out for a rigid V22 rotor in hover, and a flexible UH-60A rotor in forward flight. Emphasis is placed on understanding and characterizing the effects of high-order spatial differencing, grid resolution, and Spalart-Allmaras (SA) detached eddy simulation (DES) in predicting the rotor figure of merit (FM) and resolving the turbulent rotor wake. The FM was accurately predicted within experimental error using SA-DES. Moreover, a new adaptive mesh refinement (AMR) procedure revealed a complex and more realistic turbulent rotor wake, including the formation of turbulent structures resembling vortical worms. Time-dependent flow visualization played a crucial role in understanding the physical mechanisms involved in these complex viscous flows. The predicted vortex core growth with wake age was in good agreement with experiment. High-resolution wakes for the UH-60A in forward flight exhibited complex turbulent interactions and turbulent worms, similar to the V22. The normal force and pitching moment coefficients were in good agreement with flight-test data.
    Keywords: Aerodynamics
    Type: ICCFD7-3506 , ARC-E-DAA-TN5574 , Seventh International Conference on Computational Fluid Dynamics (ICCFD7); Jul 09, 2012 - Jul 13, 2012; Big Island, HI; United States
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  • 54
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-07-13
    Description: Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
    Keywords: Aerodynamics
    Type: E-18485-1 , Conference on Modeling Fluid FLow (CMFF''12); Sep 04, 2012 - Sep 08, 2012; Budapest; Hungary
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  • 55
    Publication Date: 2019-07-13
    Description: In 2011, the heat exchanger and refrigeration plant for NASA Glenn Research Center's Icing Research Tunnel (IRT) were upgraded. Flow quality surveys were performed in the settling chamber of the IRT in order to understand the effect that the new heat exchanger had on the flow quality upstream of the spray bars. Measurements were made of the total pressure, static pressure, total temperature, airspeed, and ow angle (pitch and yaw). These measurements were directly compared to measurements taken in 2000, after the previous heat exchanger was installed. In general, the flow quality appears to have improved with the new heat exchanger.
    Keywords: Aerodynamics
    Type: E-18455-1 , AIAA 4th Atmospheric Sciences; Jun 25, 2012 - Jun 29, 2012; New Orleans, LA; United States
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  • 56
    Publication Date: 2019-07-13
    Description: One of the primary noise sources for Open Rotor systems is the interaction of the forward rotor tip vortex and blade wake with the aft rotor. NASA has collaborated with General Electric on the testing of a new generation of low noise, counterrotating Open Rotor systems. Three-dimensional particle image velocimetry measurements were acquired in the intra-rotor gap of the Historical Baseline blade set. The velocity measurements are of sufficient resolution to characterize the tip vortex size and trajectory as well as the rotor wake decay and turbulence character. The tip clearance vortex trajectory is compared to results from previously developed models. Forward rotor wake velocity profiles are shown. Results are presented in a form as to assist numerical modeling of Open Rotor system aerodynamics and acoustics.
    Keywords: Aerodynamics
    Type: E-18418-1 , 48th AIAA Joint Propulsion Conference; Jul 30, 2012 - Aug 01, 2012; Atlanta, GA; United States
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  • 57
    Publication Date: 2019-07-13
    Description: Several comparisons of computational fluid dynamics to wind tunnel test data are shown for the purpose of code validation. The wind tunnel test, 05-CA, uses a 7.66% model of NASA's Multi-Purpose Crew Vehicle in the 11-foot test section of the Ames Unitary Plan Wind tunnel. A variety of freestream conditions over four Mach numbers and three angles of attack are considered. Test data comparisons include time-averaged integrated forces and moments, time-averaged static pressure ports on the surface, and Strouhal Number. The applicability of the US3D code to subsonic and transonic flow over a bluff body is assessed on a comprehensive data set. With close comparison, this work validates US3D for highly separated flows similar to those examined here.
    Keywords: Aerodynamics
    Type: JSC-CN-27543 , JSC-CN-27560 , 51st AIAA Aerospace Sciences Meeting; Jan 07, 2013 - Jan 10, 2013; Grapevine, TX; United States
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  • 58
    Publication Date: 2019-07-13
    Description: The structural properties of Higher harmonic Aeroacoustic Rotor Test (HART I) blades have been measured using the original set of blades tested in the wind tunnel in 1994. A comprehensive rotor dynamics analysis is performed to address the effect of the measured blade properties on airloads, blade motions, and structural loads of the rotor. The measurements include bending and torsion stiffness, geometric offsets, and mass and inertia properties of the blade. The measured properties are correlated against the estimated values obtained initially by the manufacturer of the blades. The previously estimated blade properties showed consistently higher stiffnesses, up to 30% for the flap bending in the blade inboard root section. The measured offset between the center of gravity and the elastic axis is larger by about 5% chord length, as compared with the estimated value. The comprehensive rotor dynamics analysis was carried out using the measured blade property set for HART I rotor with and without HHC (Higher Harmonic Control) pitch inputs. A significant improvement on blade motions and structural loads is obtained with the measured blade properties.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN5549 , 38th European Rotorcraft Forum 2012; Sep 04, 2012 - Sep 07, 2012; Amsterdam; Netherlands
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  • 59
    Publication Date: 2019-07-13
    Description: An innovative pressure rail concept for wind tunnel sonic boom testing of modern aircraft configurations with very low overpressures was designed with an adjoint-based solution-adapted Cartesian grid method. The computational method requires accurate free-air calculations of a test article as well as solutions modeling the influence of rail and tunnel walls. Specialized grids for accurate Euler and Navier-Stokes sonic boom computations were used on several test articles including complete aircraft models with flow-through nacelles. The computed pressure signatures are compared with recent results from the NASA 9- x 7-foot Supersonic Wind Tunnel using the advanced rail design.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN4517 , International Conference on Computational Fluid Dynamics (ICCFD7); Jul 09, 2012 - Jul 13, 2012; Big Island, HI; United States
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  • 60
    Publication Date: 2019-07-13
    Description: This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy faculties. The geometry corresponded to "Pak B" LPT airfoil. The test section simulated LPT flow in a passage. Three experimental studies were performed: (a) Boundary layer measurements for ten baseline cases under high and low freestream turbulence conditions at five Reynolds numbers of 25,000, 50,000, 100,000, 200,000, and 300,000, based on passage exit velocity and suction surface wetted length; (b) Passive flow control studies with three thicknesses of two-dimensional bars, and two heights of three-dimensional circular cylinders with different spanwise separations, at same flow conditions as the 10 baseline cases; (c) Active flow control with oscillating synthetic (zero net mass flow) vortex generator jets, for one case with low freestream turbulence and a low Reynolds number of 25,000. The Passive flow control was successful at controlling the separation problem at low Reynolds numbers, with varying degrees of success from case to case and varying levels of impact at higher Reynolds numbers. The active flow control successfully eliminated the large separation problem for the low Reynolds number case. Very detailed data was acquired using hot-wire anemometry, including single and two velocity components, integral boundary layer quantities, turbulence statistics and spectra, turbulent shear stresses and their spectra, and intermittency, documenting transition, separation and reattachment. Models were constructed to correlate the results. The report includes a summary of the work performed and reprints of the publications describing the various studies.
    Keywords: Aerodynamics
    Type: NASA/CR-2012-217656 , E-18233
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  • 61
    Publication Date: 2019-07-13
    Description: Wind tunnel measurements of the rotor trim, blade airloads, and structural loads of a full-scale UH-60A Black Hawk main rotor are compared with calculations obtained using the comprehensive rotorcraft analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. A speed sweep at constant lift up to an advance ratio of 0.4 and a thrust sweep at constant speed into deep stall are investigated. The coupled analysis shows significant improvement over comprehensive analysis. Normal force phase is better captured and pitching moment magnitudes are better predicted including the magnitude and phase of the two stall events in the fourth quadrant at the deeply stalled condition. Structural loads are, in general, improved with the coupled analysis, but the magnitude of chord bending moment is still significantly underpredicted. As there are three modes around 4 and 5/rev frequencies, the structural responses to the 5/rev airloads due to dynamic stall are magnified and thus care must be taken in the analysis of the deeply stalled condition.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN-5255 , American Helocopter Society 68th Annual Forum; May 01, 2012 - May 03, 2012; Fort Worth, TX; United States
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  • 62
    Publication Date: 2019-07-13
    Description: This paper describes the analysis of continuum static aerodynamics of Mars Science Laboratory (MSL) entry vehicle (EV). The method is derived from earlier work for Mars Exploration Rover (MER) and Mars Path Finder (MPF) and the appropriate additions are made in the areas where physics are different from what the prior entry systems would encounter. These additions include the considerations for the high angle of attack of MSL EV, ablation of the heatshield during entry, turbulent boundary layer, and other aspects relevant to the flight performance of MSL. Details of the work, the supporting data and conclusions of the investigation are presented.
    Keywords: Aerodynamics
    Type: NF1676L-14276 , 30th AIAA Applied Aerodynamics Meeting; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; Albania
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  • 63
    Publication Date: 2019-07-13
    Description: The preliminary design of multistage axial compressors in gas turbine engines is typically accomplished with mean-line methods. These methods, which rely on empirical correlations, estimate compressor performance well near the design point, but may become less reliable off-design. For land-based applications of gas turbine engines, off-design performance estimates are becoming increasingly important, as turbine plant operators desire peaking or load-following capabilities and hot-day operability. The current work develops a one-dimensional stage stacking procedure, including a newly defined blockage term, which is used to estimate the off-design performance and operability range of a 13-stage axial compressor used in a power generating gas turbine engine. The new blockage term is defined to give mathematical closure on static pressure, and values of blockage are shown to collapse to curves as a function of stage inlet flow coefficient and corrected shaft speed. In addition to these blockage curves, the stage stacking procedure utilizes stage characteristics of ideal work coefficient and adiabatic efficiency. These curves are constructed using flow information extracted from computational fluid dynamics (CFD) simulations of groups of stages within the compressor. Performance estimates resulting from the stage stacking procedure are shown to match the results of CFD simulations of the entire compressor to within 1.6% in overall total pressure ratio and within 0.3 points in overall adiabatic efficiency. Utility of the stage stacking procedure is demonstrated by estimation of the minimum corrected speed which allows stable operation of the compressor. Further utility of the stage stacking procedure is demonstrated with a bleed sensitivity study, which estimates a bleed schedule to expand the compressors operating range.
    Keywords: Aerodynamics
    Type: GT2012-69115 , E-18165 , GRC-E-DAA-TN4360 , Proceedings of the ASME Turbo Expo 2012; Jun 11, 2012 - Jun 15, 2012; Copenhagen; Denmark
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  • 64
    Publication Date: 2019-07-13
    Description: Time-dependent Navier-Stokes flow simulations have been carried out for a UH-60 rotor with simplified hub in forward flight and hover flight conditions. Flexible rotor blades and flight trim conditions are modeled and established by loosely coupling the OVERFLOW Computational Fluid Dynamics (CFD) code with the CAMRAD II helicopter comprehensive code. High order spatial differences, Adaptive Mesh Refinement (AMR), and Detached Eddy Simulation (DES) are used to obtain highly resolved vortex wakes, where the largest turbulent structures are captured. Special attention is directed towards ensuring the dual time accuracy is within the asymptotic range, and verifying the loose coupling convergence process using AMR. The AMR/DES simulation produced vortical worms for forward flight and hover conditions, similar to previous results obtained for the TRAM rotor in hover. AMR proved to be an efficient means to capture a rotor wake without a priori knowledge of the wake shape.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN5074 , AHS International 68th Annual Forum; May 01, 2012 - May 03, 2012; Forth Worth, TX; United States
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  • 65
    Publication Date: 2019-07-13
    Description: The boundary-layer transition characteristics and convective aeroheating levels on mid lift-to-drag ratio entry vehicle configurations have been studied through wind tunnel testing. Several configurations were investigated, including elliptically-blunted cylinders with both circular and elliptically-flattened cross sections, biconic geometries based on launch vehicle dual-use shrouds, and parametrically-optimized analytic geometries. Vehicles of this class have been proposed for high-mass Mars missions, such as sample return and crewed exploration, for which the conventional sphere-cone entry-vehicle geometries of previous Mars missions are insufficient. Testing was conducted at Mach 6 over a range of Reynolds numbers sufficient to generate laminar, transitional, and turbulent flow. Transition onset locations - both straight-line and cross-flow - and heating rates were obtained through global phosphor thermography. Supporting computations were performed to obtain heating rates for comparison with the data. Laminar data and predictions agreed to well within the experimental uncertainty. Fully-turbulent data and predictions also agreed well. However, in transitional flow regions, greater differences were observed. Additional aerodynamic performance data were also generated through Modified-Newtonian analyses of the geometries.
    Keywords: Aerodynamics
    Type: NF1676L-13809 , 42nd AIAA Fluid Dynamics Conference and Exhibit; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 66
    Publication Date: 2019-07-13
    Description: The slat noise from the 30P/30N high-lift system has been computed using a computational fluid dynamics code in conjunction with a Ffowcs Williams-Hawkings solver. Varying the Reynolds number from 1.71 to 12.0 million based on the stowed chord resulted in slight changes in the radiated noise. Tonal features in the spectra were robust and evident for all Reynolds numbers and even when a spanwise flow was imposed. The general trends observed in near-field fluctuations were also similar for all the different Reynolds numbers. Experiments on simplified, subscale high-lift systems have exhibited noticeable dependencies on the Reynolds number and tripping, although primarily for tonal features rather than the broadband portion of the spectra. Either the 30P/30N model behaves differently, or the computational model is unable to capture these effects. Hence, the results underscore the need for more detailed measurements of the slat cove flow.
    Keywords: Aerodynamics
    Type: NF1676L-13773 , 18th AIAA/CEAS Aeroacoustics Conference; Jun 04, 2012 - Jun 06, 2012; Colorado Springs, CO; United States
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  • 67
    Publication Date: 2019-07-13
    Description: NASA has been studying future transport concepts, envisioned to be technically realizable in the timeframe of 2020-2030, to meet environmental and performance goals. One concept receiving considerable interest involves a propulsion system embedded into a hybrid wing-body aircraft. While offering significant advantages in fuel savings and noise reduction by this concept, there are several technical challenges that are not encountered in the current fleet and must be overcome so as to deliver target performance and operability. One of these challenges is associated with an inlet system that ingests a significantly thick boundary layer, developing along the wing-body surface, into a serpentine diffuser before the flow meeting fan blades. The flow is subject to considerable total pressure loss and distorted at the fan face, much more significantly than in the inlet system of conventional aircraft. In our previous studies [1, 2], we have shown that through innovative design changes on the airframe surface, it is possible to simultaneously increase total pressure recovery and decrease distortion in the flow, without resorting to conventional penalty-ridden flow control concepts, such as vortex generator or boundary layer bleeding/suction. In the current study, we are interested in understanding the following issues: how the embedded propulsion system performs under a crosswind condition by studying in detail the flow characteristics of two inlets, the baseline and another optimized previously under the cruise condition. With the insight, it is hoped that it can help in the follow-on study by devising effective strategies to minimize flow distortion arising from the integration of an embedded-engine system into an airframe to the level acceptable to the operation and fuel consumption before 2030. To achieve these demanding goals, non-conventional concepts are called for; but technology gap is too big that it requires evolutionary approach by focusing various concepts and technologies needed in the next three generations of aircraft, respectively named as N+1, N+2, and N+3. Noticeably, considerable reduction in each category of 1 is required in N+2 (relative to Boeing 777-200 and GE90 engines) and N+3 (relative to Boeing 737-800 and CFM56-7B engines). In this study, concepts for N+2 is our interest. A concept that has potential to achieve these metrics and has been under intensive study is the hybrid wing body (HWB) airframe with a tightly integrated propulsion system, see Fig. 1. The inlet is non-circular at the entrance and the entering flow, no longer uniform or free of disturbances, and is now carrying with it a boundary layer developing along the fuselage; the inlet is thus known as boundary-layer-ingesting (BLI) inlet.
    Keywords: Aerodynamics
    Type: GT2012-68509 , E-18257 , Proceedings of ASME Turbo Expo IGTI 2012; Jun 11, 2012 - Jun 15, 2012; Copenhagen; Denmark
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  • 68
    Publication Date: 2019-07-13
    Description: The HIFiRE-1 flight experiment provided a valuable database pertaining to boundary layer transition over a 7-degree half-angle, circular cone model from supersonic to hypersonic Mach numbers, and a range of Reynolds numbers and angles of attack. This paper reports selected findings from the ongoing computational analysis of the measured in-flight transition behavior. Transition during the ascent phase at nearly zero degree angle of attack is dominated by second mode instabilities except in the vicinity of the cone meridian where a roughness element was placed midway along the length of the cone. The growth of first mode instabilities is found to be weak at all trajectory points analyzed from the ascent phase. For times less than approximately 18.5 seconds into the flight, the peak amplification ratio for second mode disturbances is sufficiently small because of the lower Mach numbers at earlier times, so that the transition behavior inferred from the measurements is attributed to an unknown physical mechanism, potentially related to step discontinuities in surface height near the locations of a change in the surface material. Based on the time histories of temperature and/or heat flux at transducer locations within the aft portion of the cone, the onset of transition correlated with a linear N-factor, based on parabolized stability equations, of approximately 13. Due to the large angles of attack during the re-entry phase, crossflow instability may play a significant role in transition. Computations also indicate the presence of pronounced crossflow separation over a significant portion of the trajectory segment that is relevant to transition analysis.
    Keywords: Aerodynamics
    Type: NF1676L-13443 , RTO AVT-200 RSM-030 Specialists'' Meeting on Hypersonic Laminar-Turbulent Transition; Apr 16, 2012 - Apr 19, 2012; San Diego, CA; United States
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  • 69
    Publication Date: 2019-07-13
    Description: Reynolds-Averaged Navier-Stokes (RANS) simulations were performed for the high-speed flowpath and isolator of a dual-flowpath Turbine-Based Combined-Cycle (TBCC) inlet using the Wind-US code. The RANS simulations were performed in preparation for the Large-scale Inlet for Mode Transition (LIMX) model tests in the NASA Glenn Research Center (GRC) 10- by 10-ft Supersonic Wind Tunnel. The LIMX inlet has a low-speed flowpath that is coupled to a turbine engine and a high-speed flowpath designed to be coupled to a Dual-Mode Scramjet (DMSJ) combustor. These RANS simulations were conducted at a simulated freestream Mach number of 4.0, which is the nominal Mach number for the planned wind tunnel testing with the LIMX model. For the simulation results presented in this paper, the back pressure, cowl angles, and freestream Mach number were each varied to assess the performance and robustness of the high-speed inlet and isolator. Under simulated wind tunnel conditions at maximum inlet mass flow rates, the high-speed flowpath pressure rise was found to be greater than a factor of four. Furthermore, at a simulated freestream Mach number of 4.0, the high-speed flowpath and isolator showed stability for freestream Mach number that drops 0.1 Mach below the design point. The RANS simulations indicate the yet-untested highspeed inlet and isolator flowpath should operate as designed. The RANS simulation results also provided important insight to researchers as they developed test plans for the LIMX experiment in GRC s 10- by 10-ft Supersonic Wind Tunnel.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217219 , E-17900 , 58th Joint Army-Navy-NASA-Air Force (JANNAF) Propulsion Meeting; Apr 18, 2011 - Apr 21, 2011; Arlington, VA
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  • 70
    Publication Date: 2019-07-13
    Description: A high fidelity analysis method is proposed to evaluate the ice accumulation and the ensuing rotor performance degradation for a helicopter flying through an icing cloud. The process uses computational fluid dynamics (CFD) coupled to a rotorcraft comprehensive code to establish the aerodynamic environment of a trimmed rotor prior to icing. Based on local aerodynamic conditions along the rotor span and accounting for the azimuthal variation, an ice accumulation analysis using NASA's Lewice3D code is made to establish the ice geometry. Degraded rotor performance is quantified by repeating the high fidelity rotor analysis with updates which account for ice shape and mass. The process is applied on a full-scale UH-1H helicopter in hover using data recorded during the Helicopter Icing Flight Test Program.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217126 , E-17815 , 66th Annual Forum and Technology Display (AHS Forum 66); May 11, 2010 - May 13, 2010; Phoenix, AZ; United States
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  • 71
    Publication Date: 2019-07-13
    Description: An icing analysis process involving the loose coupling of OVERFLOW-RCAS for rotor performance prediction and with LEWICE3D for thermal analysis and ice accretion is applied to a model-scale rotor for validation. The process offers high-fidelity rotor analysis for the noniced and iced rotor performance evaluation that accounts for the interaction of nonlinear aerodynamics with blade elastic deformations. Ice accumulation prediction also involves loosely coupled data exchanges between OVERFLOW and LEWICE3D to produce accurate ice shapes. Validation of the process uses data collected in the 1993 icing test involving Sikorsky's Powered Force Model. Non-iced and iced rotor performance predictions are compared to experimental measurements as are predicted ice shapes.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217122 , E-17811 , 67th Annual Forum and Technology Display (Forum 67); May 03, 2011 - May 05, 2011; Virginia Beach, VA; United States
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  • 72
    Publication Date: 2019-07-13
    Description: This paper documents a check standard wind tunnel test conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3M TCT) that was designed and analyzed using the Modern Design of Experiments (MDOE). The test designed to partition the unexplained variance of typical wind tunnel data samples into two constituent components, one attributable to ordinary random error, and one attributable to systematic error induced by covariate effects. Covariate effects in wind tunnel testing are discussed, with examples. The impact of systematic (non-random) unexplained variance on the statistical independence of sequential measurements is reviewed. The corresponding correlation among experimental errors is discussed, as is the impact of such correlation on experimental results generally. The specific experiment documented herein was organized as a formal test for the presence of unexplained variance in representative samples of wind tunnel data, in order to quantify the frequency with which such systematic error was detected, and its magnitude relative to ordinary random error. Levels of systematic and random error reported here are representative of those quantified in other facilities, as cited in the references.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-0764 , NF1676L-14030 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 73
    Publication Date: 2019-07-13
    Description: The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.
    Keywords: Aerodynamics
    Type: E-18047 , AIAA Aerospace Science Conference; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 74
    Publication Date: 2019-07-13
    Description: This paper provides experimental evidence and supporting computational analysis to characterize the laminar to turbulent flow transition in a high enthalpy arc-jet facility at NASA Ames Research Center. The arc-jet test data obtained in the 20 MW Panel Test Facility include measurements of surface pressure and heat flux on a water-cooled calibration plate, and measurements of surface temperature on a reaction-cured glass coated tile plate. Computational fluid dynamics simulations are performed to characterize the arc-jet test environment and estimate its parameters consistent with the facility and calibration measurements. The present analysis comprises simulations of the nonequilibrium flowfield in the facility nozzle, test box, and flowfield over test articles. Both laminar and turbulent simulations are performed, and the computed results are compared with the experimental measurements, including Stanton number dependence on Reynolds number. Comparisons of computed and measured surface heat fluxes (and temperatures), along with the accompanying analysis, confirm that that the boundary layer in the Panel Test Facility flow is transitional at certain archeater conditions.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN5382 , 43rd AIAA Thermophysics Conference; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 75
    Publication Date: 2019-07-13
    Description: In recent years, the FAA has worked with Transport Canada, National Research Council Canada (NRC) and APS Aviation, Inc. to develop allowance times for aircraft operations in ice-pellet precipitation. These allowance times are critical to ensure safety and efficient operation of commercial and cargo flights. Wind-tunnel testing with uncontaminated anti-icing fluids and fluids contaminated with simulated ice pellets had been carried out at the NRC Propulsion and Icing Wind Tunnel (PIWT) to better understand the flowoff characteristics and resulting aerodynamic effects. The percent lift loss on the thin, high-performance wing model tested in the PIWT was determined at 8 angle of attack and used as one of the evaluation criteria in determining the allowance times. Because it was unclear as to how performance degradations measured on this model were relevant to an actual airplane configuration, some means of interpreting the wing model lift loss was deemed necessary. This paper describes how the lift loss was related to the loss in maximum lift of a Boeing 737-200ADV airplane through the Aerodynamic Acceptance Test (AAT) performed for fluids qualification. A loss in maximum lift coefficient of 5.24 percent on the B737-200ADV airplane (which was adopted as the threshold in the AAT) corresponds to a lift loss of 7.3 percent on the PIWT model at 8 angle of attack. There is significant scatter in the data used to develop the correlation related to varying effects of the anti-icing fluids that were tested and other factors. A statistical analysis indicated the upper limit of lift loss on the PIWT model was 9.2 percent. Therefore, for cases resulting in PIWT model lift loss from 7.3 to 9.2 percent, extra scrutiny of the visual observations is required in evaluating fluid performance with contamination.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217701 , AIAA Paper 2012-2800 , E-18388 , 4th AIAA Atmospheric and Space Environments Conference; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 76
    Publication Date: 2019-07-13
    Description: Blade displacement measurements using multi-camera photogrammetry were acquired during the full-scale wind tunnel test of the UH-60A Airloads rotor, conducted in the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel. The objectives were to measure the blade displacement and deformation of the four rotor blades as they rotated through the entire rotor azimuth. These measurements are expected to provide a unique dataset to aid in the development and validation of rotorcraft prediction techniques. They are used to resolve the blade shape and position, including pitch, flap, lag and elastic deformation. Photogrammetric data encompass advance ratios from 0.15 to slowed rotor simulations of 1.0, thrust coefficient to rotor solidity ratios from 0.01 to 0.13, and rotor shaft angles from -10.0 to 8.0 degrees. An overview of the blade displacement measurement methodology and system development, descriptions of image processing, uncertainty considerations, preliminary results covering static and moderate advance ratio test conditions and future considerations are presented. Comparisons of experimental and computational results for a moderate advance ratio forward flight condition show good trend agreements, but also indicate significant mean discrepancies in lag and elastic twist. Blade displacement pitch measurements agree well with both the wind tunnel commanded and measured values.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN4998 , American Helicopter Society 68th Annual Forum; May 01, 2012 - May 03, 2012; Fort Worth, TX; United States
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  • 77
    Publication Date: 2019-07-13
    Description: Boundary layer transition over axisymmetric bodies at non-zero angle of attack in supersonic flow is numerically investigated as part of joint research between the National Aeronautics and Space Administration (NASA) and Japan Aerospace Exploration Agency (JAXA). Transition over four axisymmetric bodies (namely, Sears-Haack body, semi-Sears-Haack body, 5-degree straight cone and flared cone) with different axial pressure gradients has been studied at Mach 2 in order to understand the effect of axial pressure gradient on instability amplification along the leeward symmetry plane and in the region of nonzero crossflow away from it. Comparisons are made with measured transition data in Mach 2 facilities as well as with predicted and measured transition characteristics for a 5-degree straight cone in a Mach 3.5 low disturbance tunnel. Limitations of using linear stability correlations for predicting transition over axisymmetric bodies at angle of attack are pointed out.
    Keywords: Aerodynamics
    Type: NF1676L-13982 , International Conference on Computational Fluid Dynamics; Jul 09, 2012 - Jul 13, 2012; Kohala Coast, HI; United States
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  • 78
    Publication Date: 2019-07-13
    Description: Simulations of a supersonic recessed-cavity flow are performed using a hybrid large-eddy/ Reynolds-averaged simulation approach utilizing an inflow turbulence recycling procedure and hybridized inviscid flux scheme. Calorically perfect air enters the three-dimensional domain at a free stream Mach number of 2.92. Simulations are performed to assess grid sensitivity of the solution, efficacy of the turbulence recycling, and effect of the shock sensor used with the hybridized inviscid flux scheme. Analysis of the turbulent boundary layer upstream of the rearward-facing step for each case indicates excellent agreement with theoretical predictions. Mean velocity and pressure results are compared to Reynolds-averaged simulations and experimental data for each case, and these comparisons indicate good agreement on the finest grid. Simulations are repeated on a coarsened grid, and results indicate strong grid density sensitivity. The effect of turbulence recycling on the solution is illustrated by performing coarse grid simulations with and without inflow turbulence recycling. Two shock sensors, one of Ducros and one of Larsson, are assessed for use with the hybridized inviscid flux reconstruction scheme.
    Keywords: Aerodynamics
    Type: NF1676L-14837 , 42nd AIAA Fluid Dynamics Conference and Exhibit; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 79
    Publication Date: 2019-07-13
    Description: Supersonic retropropulsion was experimentally examined in the Ames Research Center 9x7-Foot Supersonic Wind Tunnel at Mach 1.8 and 2.4. The experimental model, previously designed for and tested in the Langley Research Center Unitary Plan Wind Tunnel at Mach 2.4, 3.5 and 4.6, was a 5-in diameter 70-deg sphere-cone forebody with a 9.55-in long cylindrical aftbody. The forebody was designed to accommodate up to four 4:1 area ratio nozzles, one on the model centerline and the other three on the half radius spaced 120-deg apart. Surface pressure and flow visualization were the primary measurements, including high-speed data to investigate the dynamics of the interactions between the bow and nozzle shocks. Three blowing configurations were tested with thrust coefficients up to 10 and angles of attack up to 20-deg. Preliminary results and observations from the test are provided
    Keywords: Aerodynamics
    Type: NF1676L-13817 , 42nd AIAA Fluid Dynamics Conference and Exhibit; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 80
    Publication Date: 2019-07-13
    Description: A low-speed experimental investigation has been conducted on a 5.8-percent scale Hybrid Wing Body configuration in the NASA Langley 14- by 22-Foot Subsonic Tunnel. This Hybrid Wing Body (HWB) configuration was designed with specific intention to support the NASA Environmentally Responsible Aviation (ERA) Project goals of reduced noise, emissions, and fuel burn. This HWB configuration incorporates twin, podded nacelles mounted on the vehicle upper surface between twin vertical tails. Low-speed aerodynamic characteristics were assessed through the acquisition of force and moment, surface pressure, and flow visualization data. Longitudinal and lateral-directional characteristics were investigated on this multi-component model. The effects of a drooped leading edge, longitudinal flow-through nacelle location, vertical tail shape and position, elevon deflection, and rudder deflection have been studied. The basic configuration aerodynamics, as well as the effects of these configuration variations, are presented in this paper.
    Keywords: Aerodynamics
    Type: NF1676L-13738 , 30th AIAA Applied Aerodynamics Meeting; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 81
    Publication Date: 2019-07-13
    Description: Measurements have been conducted at the University of Virginia Supersonic Combustion Facility of the flow in a constant area duct downstream of a Mach 2 nozzle, where the airflow has first been heated to approximately 1200 K. Dual-pump CARS was used to acquire rotational and vibrational temperatures of N2 and O2 at two planes in the duct at different downstream distances from the nozzle exit. Wall static pressures in the nozzle are also reported. With a flow of clean air, the vibrational temperature of N2 freezes at close to the heater stagnation temperature, while the O2 vibrational temperature is about 1000 K. The results are well predicted by computational fluid mechanics models employing separate "lumped" vibrational and translational/rotational temperatures. Experimental results are also reported for a few percent steam addition to the air and the effect of the steam is to bring the flow to thermal equilibrium.
    Keywords: Aerodynamics
    Type: NF1676L-13801 , 28th Aerodynamic Measurement Technology, Ground Testing, and Flight Testing Conference; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 82
    Publication Date: 2019-07-13
    Description: Experimental evidence indicates the presence of a triad resonance interaction between traveling crossflow modes in a swept wing flow. Results indicate that this interaction occurs when the stationary and traveling crossflow modes have similar and relatively low amplitudes (approx.1% to 6% of the total freestream velocity). The resonant interaction occurs at instability amplitudes well below those typically known to cause transition, yet transition is observed to occur just downstream of the resonance. In each case, two primary linearly unstable traveling crossflow modes are nonlinearly coupled to a higher frequency linearly stable mode at the sum of their frequencies. The higher-frequency mode is linearly stable and presumed to exist as a consequence of the interaction of the two primary modes. Autoand cross-bicoherence are used to determine the extent of phase-matching between the modes, and wavenumber matching confirms the triad resonant nature of the interaction. The bicoherence results indicate a spectral broadening mechanism and the potential path to early transition. The implications for laminar flow control in swept wing flows are significant. Even if stationary crossflow modes remain subcritical, traveling crossflow interactions can lead to early transition.
    Keywords: Aerodynamics
    Type: NF1676L-13793 , 42nd AIAA Fluid Dynamics Conference and Exhibit; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 83
    Publication Date: 2019-07-13
    Description: Measurements of mean and instantaneous streamwise velocity profiles in a hypersonic boundary layer with variable rates of mass injection (blowing) of nitrogen dioxide (NO2) were obtained over a 10-degree half-angle wedge model. The NO2 was seeded into the flow from a slot located 29.4 mm downstream of the sharp leading edge. The top surface of the wedge was oriented at a 20 degree angle in the Mach 10 flow, yielding an edge Mach number of approximately 4.2. The streamwise velocity profiles and streamwise fluctuating velocity component profiles were obtained using a three-laser NO2-〉NO photolysis molecular tagging velocimetry method. Observed trends in the mean streamwise velocity profiles and profiles of the fluctuating component of streamwise velocity as functions of the blowing rate are described. An effort is made to distinguish between the effect of blowing rate and wall temperature on the measured profiles. An analysis of the mean velocity profiles for a constant blowing rate is presented to determine the uncertainty in the measurement for different probe laser delay settings. Measurements of streamwise velocity were made to within approximately 120 gm of the model surface. The streamwise spatial resolution in this experiment ranged from 0.6 mm to 2.6 mm. An improvement in the spatial precision of the measurement technique has been made, with spatial uncertainties reduced by about a factor of 2 compared to previous measurements. For the quiescent flow calibration measurements presented, uncertainties as low as 2 m/s are obtained at 95% confidence for long delay times (25 gs). For the velocity measurements obtained with the wind tunnel operating, average single-shot uncertainties of less than 44 m/s are obtained at 95% confidence with a probe laser delay setting of 1 gs. The measurements were performed in the 31-inch Mach 10 Air Tunnel at the NASA Langley Research Center.
    Keywords: Aerodynamics
    Type: NF1676L-13805 , 42nd AIAA Fluid Dynamics Conference and Exhibit; Jun 25, 2012 - Jun 28, 2012; New Orleans, LA; United States
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  • 84
    Publication Date: 2019-07-13
    Description: The design of entry vehicles requires predictions of aerothermal environment during the hypersonic phase of their flight trajectories. These predictions are made using computational fluid dynamics (CFD) codes that often rely on physics and chemistry models of nonequilibrium processes. The primary processes of interest are gas phase chemistry, internal energy relaxation, electronic excitation, nonequilibrium emission and absorption of radiation, and gas-surface interaction leading to surface recession and catalytic recombination. NASAs Hypersonics Project is advancing the state-of-the-art in modeling of nonequilibrium phenomena by making detailed spectroscopic measurements in shock tube and arcjets, using ab-initio quantum mechanical techniques develop fundamental chemistry and spectroscopic databases, making fundamental measurements of finite-rate gas surface interactions, implementing of detailed mechanisms in the state-of-the-art CFD codes, The development of new models is based on validation with relevant experiments. We will present the latest developments and a roadmap for the technical areas mentioned above
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN4625 , 50th AIAA Aerospace Sciences Meeting; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 85
    Publication Date: 2019-07-13
    Description: Second mode disturbances dominate the primary instability stage of transition in a number of hypersonic flow configurations. The highest amplification rates of second mode disturbances are usually associated with 2D (or axisymmetric) perturbations and, therefore, a likely scenario for the onset of the three-dimensionality required for laminar-turbulent transition corresponds to the parametric amplification of 3D secondary instabilities in the presence of 2D, finite amplitude second mode disturbances. The secondary instability of second mode disturbances is studied for selected canonical flow configurations. The basic state for the secondary instability analysis is obtained by tracking the linear and nonlinear evolution of 2D, second mode disturbances using nonlinear parabolized stability equations. Unlike in previous studies, the selection of primary disturbances used for the secondary instability analysis was based on their potential relevance to transition in a low disturbance environment and the effects of nonlinearity on the evolution of primary disturbances was accounted for. Strongly nonlinear effects related to the self-interaction of second mode disturbances lead to an upstream shift in the upper branch neutral location. Secondary instability computations confirm the previously known dominance of subharmonic modes at relatively small primary amplitudes. However, for the Purdue Mach 6 compression cone configuration, it was shown that a strong fundamental secondary instability can exist for a range of initial amplitudes of the most amplified second mode disturbance, indicating that the exclusive focus on subharmonic modes in the previous applications of secondary instability theory to second mode primary instability may not have been fully justified.
    Keywords: Aerodynamics
    Type: NF1676L-13407 , RTO AVT-200 RSM-030 Specialists'' Meeting on Hypersonic Laminar-Turbulent Transition; Apr 16, 2012 - Apr 19, 2012; San Diego, CA; United States
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  • 86
    Publication Date: 2019-07-13
    Description: Hybrid flow control, a combination of micro-ramps and micro-jets, was experimentally investigated in the 15x15 cm Supersonic Wind Tunnel (SWT) at the NASA Glenn Research Center. Full factorial, a design of experiments (DOE) method, was used to develop a test matrix with variables such as inter-ramp spacing, ramp height and chord length, and micro-jet injection flow ratio. A total of 17 configurations were tested with various parameters to meet the DOE criteria. In addition to boundary-layer measurements, oil flow visualization was used to qualitatively understand shock induced flow separation characteristics. The flow visualization showed the normal shock location, size of the separation, path of the downstream moving counter-rotating vortices, and corner flow effects. The results show that hybrid flow control demonstrates promise in reducing the size of shock boundary-layer interactions and resulting flow separation by means of energizing the boundary layer.
    Keywords: Aerodynamics
    Type: E-18161 , 50th AIAA Aerospace Sciences Meeting; Jan 07, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 87
    Publication Date: 2019-07-13
    Description: Wind-tunnel research was recently conducted at the NASA Langley Research Center s 31-Inch Mach 10 Hypersonic Facility in support of the Mars Science Laboratory s aerodynamic program. Researchers were interested in understanding the interaction between the freestream flow and the reaction control system onboard the entry vehicle. A five-component balance, designed for hypersonic testing with pressurized flow-through capability, was used. In addition to the aerodynamic forces, the balance was exposed to both thermal gradients and varying internal cavity pressures. Historically, the effect of these environmental conditions on the response of the balance have not been fully characterized due to the limitations in the calibration facilities. Through statistical design of experiments, thermal and pressure effects were strategically and efficiently integrated into the calibration of the balance. As a result of this new approach, researchers were able to use the balance continuously throughout the wide range of temperatures and pressures and obtain real-time results. Although this work focused on a specific application, the methodology shown can be applied more generally to any force measurement system calibration.
    Keywords: Aerodynamics
    Type: AIAA Paper 2011-950 , NF1676L-14582 , NF1676L-12895 , Journal of Aircract; 49; 2; 556-565|49th AiAA Aerospace Sciences Meeting; Jan 04, 2011 - Jan 07, 2011; Orlando, FL; United States
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  • 88
    Publication Date: 2019-07-13
    Description: An experimental research effort was begun to develop a database of airplane aerodynamic characteristics with simulated ice accretion over a large range of incidence and sideslip angles. Wind-tunnel testing was performed at the NASA Langley 12-ft Low-Speed Wind Tunnel using a 3.5 percent scale model of the NASA Langley Generic Transport Model. Aerodynamic data were acquired from a six-component force and moment balance in static-model sweeps from alpha = -5deg to 85deg and beta = -45 deg to 45 deg at a Reynolds number of 0.24 x10(exp 6) and Mach number of 0.06. The 3.5 percent scale GTM was tested in both the clean configuration and with full-span artificial ice shapes attached to the leading edges of the wing, horizontal and vertical tail. Aerodynamic results for the clean airplane configuration compared favorably with similar experiments carried out on a 5.5 percent scale GTM. The addition of the large, glaze-horn type ice shapes did result in an increase in airplane drag coefficient but had little effect on the lift and pitching moment. The lateral-directional characteristics showed mixed results with a small effect of the ice shapes observed in some cases. The flow visualization images revealed the presence and evolution of a spanwise-running vortex on the wing that was the dominant feature of the flowfield for both clean and iced configurations. The lack of ice-induced performance and flowfield effects observed in this effort was likely due to Reynolds number effects for the clean configuration. Estimates of full-scale baseline performance were included in this analysis to illustrate the potential icing effects.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217246 , SAE-2011-38-0065 , E-18002 , International Conference on Aircraft and Engine Icing and Ground Deicing; Jun 13, 2011 - Jun 17, 2011; Chicago, IL; United States
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  • 89
    Publication Date: 2019-07-13
    Description: Direct numerical simulations of spatially developing turbulent boundary layers over riblets are conducted to examine the effects of riblets on skin friction at supersonic speeds. Zero-pressure gradient boundary layers with an adiabatic wall, a Mach number of M1 = 2.5, and a Reynolds number based on momentum thickness of Re = 1720 are considered. Simulations are conducted for boundary-layer flows over a clean surface and symmetric V- groove riblets with nominal spacings of 20 and 40 wall units. The DNS results confirm the few existing experimental observations and show that a drag reduction of approximately 7% is achieved for riblets with proper spacing. The influence of riblets on turbulence statistics is analyzed in detail with an emphasis on identifying the differences, if any, between the drag reduction mechanisms for incompressible and high-speed boundary layers.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1108 , NF1676L-12818 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 90
    Publication Date: 2019-07-13
    Description: When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-0081 , NF1676L-12936 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 91
    Publication Date: 2019-07-13
    Description: A 2D circulation control wing was tested in the Basic Aerodynamic Research Tunnel at the NASA Langley Research Center. A traditional circulation control wing employs tangential blowing along the span over a trailing-edge Coanda surface for the purpose of lift augmentation. This model has been tested extensively at the Georgia Tech Research Institute for the purpose of performance documentation at various blowing rates. The current study seeks to expand on the previous work by documenting additional flow-field data needed for validation of computational fluid dynamics. Two jet momentum coefficients were tested during this entry: 0.047 and 0.114. Boundary-layer transition was investigated and turbulent boundary layers were established on both the upper and lower surfaces of the model. Chordwise and spanwise pressure measurements were made, and tunnel sidewall pressure footprints were documented. Laser Doppler Velocimetry measurements were made on both the upper and lower surface of the model at two chordwise locations (x/c = 0.8 and 0.9) to document the state of the boundary layers near the spanwise blowing slot.
    Keywords: Aerodynamics
    Type: AIAA 2012-0705 , NF1676L-12904 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 92
    Publication Date: 2019-07-13
    Description: An experimental investigation of the NASA Common Research Model was conducted in the NASA Langley National Transonic Facility and NASA Ames 11-Foot Transonic Wind Tunnel Facility for use in the Drag Prediction Workshop. As data from the experimental investigations was collected, a large difference in moment values was seen between the experimental and the computational data from the 4th Drag Prediction Workshop. This difference led to the present work. In this study, a computational assessment has been undertaken to investigate model support system interference effects on the Common Research Model. The configurations computed during this investigation were the wing/body/tail=0deg without the support system and the wing/body/tail=0deg with the support system. The results from this investigation confirm that the addition of the support system to the computational cases does shift the pitching moment in the direction of the experimental results.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-0707 , NF1676L-12888 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 93
    Publication Date: 2019-07-12
    Description: No abstract available
    Keywords: Aerodynamics
    Type: JSC-CN-27575
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  • 94
    Publication Date: 2019-07-12
    Description: New first- and second-order displacement transfer functions have been developed for deformed shape calculations of nonuniform cross-sectional beam structures such as aircraft wings. The displacement transfer functions are expressed explicitly in terms of beam geometrical parameters and surface strains (uniaxial bending strains) obtained at equally spaced strain stations along the surface of the beam structure. By inputting the measured or analytically calculated surface strains into the displacement transfer functions, one could calculate local slopes, deflections, and cross-sectional twist angles of the nonuniform beam structure for mapping the overall structural deformed shapes for visual display. The accuracy of deformed shape calculations by the first- and second-order displacement transfer functions are determined by comparing these values to the analytically predicted values obtained from finite element analyses. This comparison shows that the new displacement transfer functions could quite accurately calculate the deformed shapes of tapered cantilever tubular beams with different tapered angles. The accuracy of the present displacement transfer functions also are compared to those of the previously developed displacement transfer functions.
    Keywords: Aerodynamics
    Type: NASA/TP-2012-215976 , DFRC-1094 , DFRC-E-DAA-TN3870
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  • 95
    Publication Date: 2019-07-12
    Description: This publication is the final report of research performed under an NRA/Cooperative Interagency Agreement, and includes a supplemental CD-ROM with detailed data. It is complemented by NASA/CR-2012-217416 and NASA/CR-2012-217417 which include a Ph.D. Dissertation and an M.S. thesis respectively, performed under this contract. In this study the effects of unsteady wakes and flow control using vortex generator jets (VGJs) were studied experimentally and computationally on the flow over the L1A low pressure turbine (LPT) airfoil. The experimental facility was a six passage linear cascade in a low speed wind tunnel at the U.S. Naval Academy. In parallel, computational work using the commercial code FLUENT (ANSYS, Inc.) was performed at Cleveland State University, using Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy Simulations (LES) methods. In the first phase of the work, the baseline flow was documented under steady inflow conditions without flow control. URANS calculations were done using a variety of turbulence models. In the second phase of the work, flow control was added using steady and pulsed vortex generator jets. The VGJs successfully suppressed separation and reduced aerodynamic losses. Pulsed operation was more effective and mass flow requirements are very low. Numerical simulations of the VGJs cases showed that URANS failed to capture the effect of the jets. LES results were generally better. In the third phase, effects of unsteady wakes were studied. Computations with URANS and LES captured the wake effect and generally predicted separation and reattachment to match the experiments. Quantitatively the results were mixed. In the final phase of the study, wakes and VGJs were combined and synchronized using various timing schemes. The timing of the jets with respect to the wakes had some effect, but in general once the disturbance frequency was high enough to control separation, the timing was not very important. This is the supplemental CD-ROM
    Keywords: Aerodynamics
    Type: NASA/CR-2012-217415/SUPPL , E-18086
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  • 96
    Publication Date: 2019-07-12
    Description: Numerical predictions of the longitudinal aerodynamic characteristics for the Ares I class of vehicles, along with the associated error estimate derived from an iterative convergence grid refinement, are presented. Computational results are based on an unstructured grid, Reynolds-averaged Navier-Stokes analysis. The validity of the approach to compute the associated error estimates, derived from a base grid to an extrapolated infinite-size grid, was first demonstrated on a sub-scaled wind tunnel model at representative ascent flow conditions for which the experimental data existed. Such analysis at the transonic flow conditions revealed a maximum deviation of about 23% between the computed longitudinal aerodynamic coefficients with the base grid and the measured data across the entire roll angles. This maximum deviation from the wind tunnel data was associated with the computed normal force coefficient at the transonic flow condition and was reduced to approximately 16% based on the infinite-size grid. However, all the computed aerodynamic coefficients with the base grid at the supersonic flow conditions showed a maximum deviation of only about 8% with that level being improved to approximately 5% for the infinite-size grid. The results and the error estimates based on the established procedure are also presented for the flight flow conditions.
    Keywords: Aerodynamics
    Type: NF1676L-13540
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  • 97
    Publication Date: 2019-07-12
    Description: An experimental investigation was conducted in the NASA Langley 7 x 10-Foot High Speed Tunnel (HST) to study the effect of leading- and trailing-edge sweep on cavity flow fields for a range of cavity length-to-height (l/h) ratios. The free-stream Mach number was varied from 0.2 to 0.8. The cavity had a depth of 0.5 inches, a width of 2.5 inches, and a maximum length of 12.0 inches. The leading- and trailing-edge sweep was adjusted using block inserts to achieve leading edge sweep angles of 65 deg, 55 deg, 45 deg, 35 deg, and 0 deg. The fore and aft cavity walls were always parallel. The aft wall of the cavity was remotely positioned to achieve a range of length-to-depth ratios. Fluctuating- and static-pressure data were obtained on the floor of the cavity. The fluctuating pressure data were used to determine whether or not resonance occurred in the cavity rather than to provide a characterization of the fluctuating pressure field. Qualitative surface flow visualization was obtained using a technique in which colored water was introduced into the model through static-pressure orifices. A complete tabulation of the mean static-pressure data for the swept leading edge cavities is included.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217577 , NF1676L-13087 , L-20047
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  • 98
    Publication Date: 2019-07-12
    Description: Flow field survey results for the effect of ramp-shaped vortex generators (VG) on a turbulent boundary layer are presented. The experiments are carried out in a low-speed wind tunnel and the data are acquired primarily by hot-wire anemometry. Distributions of mean velocity and turbulent stresses as well as streamwise vorticity, on cross-sectional planes at various downstream locations, are obtained. These detailed flow field properties, including the boundary layer characteristics, are documented with the primary objective of aiding possible computational investigations. The results show that VG orientation with apex upstream, that produces a downwash directly behind it, yields a stronger pair of streamwise vortices. This is in contrast to the case with apex downstream that produces a pair of vortices of opposite sense. Thus, an array of VG s with the former orientation, usually considered for film-cooling application, may also be superior for mixing enhancement and boundary layer separation control. (See CASI ID 20120009374 for Supplemental CD-ROM.)
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217437 , E-18130
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  • 99
    Publication Date: 2019-07-12
    Description: A 15-percent-thick, slotted, natural-laminar-flow (SNLF) airfoil, the S103, for general aviation applications has been designed and analyzed theoretically and verified experimentally in the Langley Low-Turbulence Pressure Tunnel. The two primary objectives of high maximum lift and low profile drag have been achieved. The constraints on the pitching moment and the airfoil thickness have been satisfied. The airfoil exhibits a rapid stall, which does not meet the design goal. Comparisons of the theoretical and experimental results show good agreement. Comparison with the baseline, NASA NLF(1)-0215F airfoil confirms the achievement of the objectives.
    Keywords: Aerodynamics
    Type: NASA/CR-2012-217560 , NF1676L-14322
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  • 100
    Publication Date: 2019-07-12
    Description: This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
    Keywords: Aerodynamics
    Type: NASA/CR-2012-217331 , NF1676L-14090
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