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  • 1
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    Application of the space-time conservation element and solution element method to two-dimensional advection-diffusion problems (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The existing 2-D alpha-mu scheme and alpha-epsilon scheme based on the method of space-time conservation element and solution element, which were constructed for solving the linear 2-D unsteady advection-diffusion equation and unsteady advection equation, respectively, are tested. Also, the alpha-epsilon scheme is modified to become the V-E scheme for solving the nonlinear 2-D inviscid Burgers equation. Numerical solutions of six test problems are presented in comparison with their exact solutions or numerical solutions obtained by traditional finite-difference or finite-element methods. It is demonstrated that the 2-D alpha-mu, alpha-epsilon, and nu-epsilon schemes can be used to obtain numerical results which are more accurate than those based on some of the traditional methods but without using any artificial tuning in the computation. Similar to the previous 1-D test problems, the high accuracy and simplicity features of the space-time conservation element and solution element method have been revealed again in the present 2-D test results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106946 , E-9681 , NAS 1.15:106946
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    NASA TECHNICAL REPORTS
  • 2
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    Application of the space-time conservation element and solution element method to shock-tube problem (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An Euler solver based on the method of space-time conservation element and solution element is in this paper to simulate shock-tube flows involving shock waves, contact discontinuities, expansion waves and their intersections. Seven test problems are considered to examine the capability of this method. The numerical results, when compared with exact solutions and/or numerical solutions by other methods, indicate that the present method can accurately resolve strong shock and contact discontinuities without using any ad hoc techniques which are used only at the neighborhood of a discontinuity.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106806 , E-9288 , NAS 1.15:106806
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    NASA TECHNICAL REPORTS
  • 3
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    The method of space-time conservation element and solution element-applications to one-dimensional and two-dimensional time-marching flow problems (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A nontraditional numerical method for solving conservation laws is being developed. The new method is designed from a physicist's perspective, i.e., its development is based more on physics than numerics. Even though it uses only the simplest approximation techniques, a 2D time-marching Euler solver developed recently using the new method is capable of generating nearly perfect solutions for a 2D shock reflection problem used by Helen Yee and others. Moreover, a recent application of this solver to computational aeroacoustics (CAA) problems reveals that: (1) accuracy of its results is comparable to that of a 6th order compact difference scheme even though nominally the current solver is only of 2nd-order accuracy; (2) generally, the non-reflecting boundary condition can be implemented in a simple way without involving characteristic variables; and (3) most importantly, the current solver is capable of handling both continuous and discontinuous flows very well and thus provides a unique numerical tool for solving those flow problems where the interactions between sound waves and shocks are important, such as the noise field around a supersonic over- or under-expansion jet.
    Keywords: NUMERICAL ANALYSIS
    Type: NASA-TM-106915 , E-9623 , NAS 1.15:106915 , AIAA PAPER 95-1754 , Annual Maryland Conference on The Evolution of X-ray Binaries; Jun 19, 1995 - Jun 22, 1995; San Diego, CA; United States
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  • 4
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    High Resolution Euler Solvers Based on the Space-Time Conservation Element and Solution Element Method (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The I-D, quasi I-D and 2-D Euler solvers based on the method of space-time conservation element and solution element are used to simulate various flow phenomena including shock waves, Mach stem, contact surface, expansion waves, and their intersections and reflections. Seven test problems are solved to demonstrate the capability of this method for handling unsteady compressible flows in various configurations. Numerical results so obtained are compared with exact solutions and/or numerical solutions obtained by schemes based on other established computational techniques. Comparisons show that the present Euler solvers can generate highly accurate numerical solutions to complex flow problems in a straightforward manner without using any ad hoc techniques in the scheme.
    Keywords: Numerical Analysis
    Type: NASA/CR-96-207329 , NAS 1.26:207329 , AIAA Paper-96-0764 , Aerospace Sciences; Jan 15, 1996 - Jan 18, 1996; Reno, NV; United States
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  • 5
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    The Space-Time Conservation Element and Solution Element Method: A New High-Resolution and Genuinely Multidimensional Paradigm for Solving Conservation Laws (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A new high resolution and genuinely multidimensional numerical method for solving conservation laws is being, developed. It was designed to avoid the limitations of the traditional methods. and was built from round zero with extensive physics considerations. Nevertheless, its foundation is mathmatically simple enough that one can build from it a coherent, robust. efficient and accurate numerical framework. Two basic beliefs that set the new method apart from the established methods are at the core of its development. The first belief is that, in order to capture physics more efficiently and realistically, the modeling, focus should be placed on the original integral form of the physical conservation laws, rather than the differential form. The latter form follows from the integral form under the additional assumption that the physical solution is smooth, an assumption that is difficult to realize numerically in a region of rapid chance. such as a boundary layer or a shock. The second belief is that, with proper modeling of the integral and differential forms themselves, the resulting, numerical solution should automatically be consistent with the properties derived front the integral and differential forms, e.g., the jump conditions across a shock and the properties of characteristics. Therefore a much simpler and more robust method can be developed by not using the above derived properties explicitly.
    Keywords: Mathematical and Computer Sciences (General)
    Type: NASA/TM-1998-208843 , E-11456 , NAS 1.15:208843
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  • 6
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    The Space-Time Conservation Element and Solution Element Method-A New High-Resolution and Genuinely Multidimensional Paradigm for Solving Conservation Laws (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Without resorting to special treatment for each individual test case, the 1D and 2D CE/SE shock-capturing schemes described previously (in Part I) are used to simulate flows involving phenomena such as shock waves, contact discontinuities, expansion waves and their interactions. Five 1D and six 2D problems are considered to examine the capability and robustness of these schemes. Despite their simple logical structures and low computational cost (for the 2D CE/SE shock-capturing scheme, the CPU time is about 2 micro-secs per mesh point per marching step on a Cray C90 machine), the numerical results, when compared with experimental data, exact solutions or numerical solutions by other methods, indicate that these schemes can accurately resolve shock and contact discontinuities consistently.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA/TM-1998-208844 , E-11457 , NAS 1.15:208844
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  • 7
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    Application of the Space-Time Conservation Element and Solution Element Method to One-Dimensional Advection-Diffusion Problems (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Test problems are used to examine the performance of several one-dimensional numerical schemes based on the space-time conservation and solution element (CE/SE) method. Investigated in this paper are the CE/SE schemes constructed previously for solving the linear unsteady advection-diffusion equation and the schemes derived here for solving the nonlinear viscous and inviscid Burgers equations. In comparison with the numerical solutions obtained using several traditional finite-difference schemes with similar accuracy, the CE/SE solutions display much lower numerical dissipation and dispersion errors.
    Keywords: Numerical Analysis
    Type: NASA/TM-1999-209068 , NAS 1.15:209068 , E-11624
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  • 8
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    New Developments in the Method of Space-Time Conservation Element and Solution Element-Applications to Two-Dimensional Time-Marching Problems (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A new numerical discretization method for solving conservation laws is being developed. This new approach differs substantially in both concept and methodology from the well-established methods, i.e., finite difference, finite volume, finite element, and spectral methods. It is motivated by several important physical/numerical considerations and designed to avoid several key limitations of the above traditional methods. As a result of the above considerations, a set of key principles for the design of numerical schemes was put forth in a previous report. These principles were used to construct several numerical schemes that model a 1-D time-dependent convection-diffusion equation. These schemes were then extended to solve the time-dependent Euler and Navier-Stokes equations of a perfect gas. It was shown that the above schemes compared favorably with the traditional schemes in simplicity, generality, and accuracy. In this report, the 2-D versions of the above schemes, except the Navier-Stokes solver, are constructed using the same set of design principles. Their constructions are simplified greatly by the use of a nontraditional space-time mesh. Its use results in the simplest stencil possible, i.e., a tetrahedron in a 3-D space-time with a vertex at the upper time level and other three at the lower time level. Because of the similarity in their design, each of the present 2-D solvers virtually shares with its 1-D counterpart the same fundamental characteristics. Moreover, it is shown that the present Euler solver is capable of generating highly accurate solutions for a famous 2-D shock reflection problem. Specifically, both the incident and the reflected shocks can be resolved by a single data point without the presence of numerical oscillations near the discontinuity.
    Keywords: NUMERICAL ANALYSIS
    Type: NASA-TM-106758 , E-9180 , NAS 1.15:106758
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  • 9
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    ATPase activity, proton gradients and proton secretion inhibition during experiments with Sepia officinalis and Sepioteuthis lessoniana (2015)
    PANGAEA
    In:  Supplement to: Hu, Marian Y; Tseng, Yung-Che; Lin, Li-Yih; Chen, Po-Yen; Charmantier-Daures, Mireille; Hwang, Pung-Pung; Melzner, Frank (2011): New insights into ion regulation of cephalopod molluscs: a role of epidermal ionocytes in acid-base regulation during embryogenesis. American Journal of Physiology-Regulatory Integrative and Comparative Physiology, 301(6), R1700-R1709, https://doi.org/10.1152/ajpregu.00107.2011
    Details
    Publication Date: 2023-01-13
    Description: The constraints of an active life in a pelagic habitat led to numerous convergent morphological and physiological adaptations that enable cephalopod molluscs and teleost fishes to compete for similar resources. Here, we show for the first time that such convergent developments are also found in the ontogenetic progression of ion regulatory tissues; as in teleost fish, epidermal ionocytes scattered on skin and yolk sac of cephalopod embryos appear to be responsible for ionic and acid-base regulation before gill epithelia become functional. Ion and acid-base regulation is crucial in cephalopod embryos, as they are surrounded by a hypercapnic egg fluid with a Pco2 between 0.2 and 0.4 kPa. Epidermal ionocytes were characterized via immunohistochemistry, in situ hybridization, and vital dye-staining techniques. We found one group of cells that is recognized by concavalin A and MitoTracker, which also expresses Na+/H+ exchangers (NHE3) and Na+-K+-ATPase. Similar to findings obtained in teleosts, these NHE3-rich cells take up sodium in exchange for protons, illustrating the energetic superiority of NHE-based proton excretion in marine systems. In vivo electrophysiological techniques demonstrated that acid equivalents are secreted by the yolk and skin integument. Intriguingly, epidermal ionocytes of cephalopod embryos are ciliated as demonstrated by scanning electron microscopy, suggesting a dual function of epithelial cells in water convection and ion regulation. These findings add significant knowledge to our mechanistic understanding of hypercapnia tolerance in marine organisms, as it demonstrates that marine taxa, which were identified as powerful acid-base regulators during hypercapnic challenges, already exhibit strong acid-base regulatory abilities during embryogenesis.
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 10
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    Wet dissolved carbon concentration during the concentrated rainfall season (July-September, 2015) in Yangjuangou Catchment, Loess Plateau (2018)
    PANGAEA
    Details
    Publication Date: 2023-01-13
    Description: Wet dissolved carbon deposition is a critical node of the global carbon cycle, but little is known about dissolved organic and inorganic carbon (DOC and DIC) concentrations and fluxes in the semi-arid areas of the Loess Plateau Region (LPR). In this study, we measured variations of DOC and DIC concentration in rainfalls at Yangjuangou Ecological Restoration and Soil and Water Observatory. Rainwater samples were collected in 16 rainfall events from July to September and the event-based, monthly concentrations and fluxes of DOC and DIC were quantified. The results showed that the event-based concentrations and fluxes of DOC and DIC were highly variable, ranging from 0.56 to 28.71 mg C L⁻¹ and from 3.47 to 17.49 mg C L⁻¹, respectively. The corresponding event-based fluxes ranged from 0.21-258.36 mg C m⁻² and from 4.12 to 42.32 mg C m⁻². The monthly concentrations of DOC and DIC were 24.62 and 4.30 (July), 3.58 and 10.52 (August), 1.01 and 5.89 (September) mg C L⁻¹, respectively. Thus, the monthly deposition fluxes of DOC and DIC were 541.64/94.60, 131.03/385.03, and 44.44/259.16 mg C m⁻² for July, August and September, respectively. In addition, the concentrations of DOC and DIC for the concentrated rainfall season (July-September) in the studied catchment were 7.06 and 7.00 mg C L⁻¹, respectively. The estimated annual wet dissolved carbon depositions were 1.91 and 1.89 g C m⁻² yr⁻¹ for DOC and DIC, respectively. The results of this study suggest the variation in concentrations and fluxes of DOC and DIC and explored that these variation may be related to the dissolved carbon source and the rainfall characteristics during the concentrated rainfall season in the semi-arid catchment of the LPR. Furthermore, these results also suggest that dissolved carbon may be an important external input of carbon into terrestrial ecosystems.
    Keywords: China; Yanan, Shaanxi Province; Yangjuangou_catchment
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
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