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71.
Vincent Guinot 《国际流体数值方法杂志》2001,37(3):341-359
Godunov‐type algorithms are very attractive for the numerical solution of discontinuous flows. The reconstruction of the profile inside the cells is crucial to scheme performance. The non‐linear generalization of the discontinuous profile method (DPM) presented here for the modelling of two‐phase flow in pipes uses a discontinuous reconstruction in order to capture shocks more efficiently than schemes using continuous functions. The reconstructed profile is used to define the Riemann problem at cell interfaces by averaging of the components of the variable in the base of eigenvectors over their domain of dependence. Intercell fluxes are computed by solving the Riemann problem with an approximate‐state solver. The adapted treatment of boundary conditions is essential to ensure the quality of the computational results and a specific procedure using virtual cells at both extremities of the computational domain is required. Internal boundary conditions can be treated in the same way as external ones. Application of the DPM to test cases is shown to improve the quality of computational results significantly. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
72.
Paola Fisicaro Soraya Amarouche Béatrice Lalere Guillaume Labarraque Marc Priel 《Accreditation and quality assurance》2008,13(7):361-366
Since the advent of the Guide to the Expression of Uncertainty in Measurement (GUM) founding the principles of uncertainty
evaluation, numerous projects have been carried out to develop alternative practical methods when it is impossible to model
technical or economical aspects of the measurement process. These methods can use all the experimental data available to the
laboratories, such as repeatability, reproducibility, quality-control charts, etc. The studies presented in this paper compare
the results obtained by the modelling method from GUM with the uncertainties found by applying alternative methods. They show
two examples, one in the field of environmental monitoring, the other in the biomedical field, based on the exploitation of
PT schemes results.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
73.
K. N. Volkov 《Computational Mathematics and Mathematical Physics》2008,48(7):1181-1202
An unstructured-grid discretization of the Navier-Stokes equations based on the finite volume method and high-resolution difference schemes in time and space is described as applied to fluid dynamics problems in two and three dimensions. The control volume is defined as the cell-vertex median dual control volume. The fluxes through the faces of internal and boundary control volumes are written identically, which simplifies their software implementation. The gradient and the pseudo-Laplacian are calculated at the midpoint of a control volume face by using relations adapted to the computations on a strongly stretched grid in the boundary layer. 相似文献
74.
B. N. Chetverushkin E. V. Shilnikov 《Computational Mathematics and Mathematical Physics》2008,48(2):295-305
A parallel software package designed for the numerical simulation of three-dimensional viscous gas flows is presented. The numerical algorithm is based on kinetically consistent difference schemes used on locally refined grids. The software package has been tested in various super-and subsonic flow problems. It provides an opportunity for the direct simulation of turbulent flows. The efficiency of parallelization is analyzed depending on the problem size and the number of processors. 相似文献
75.
M. M. Lafisheva M. Kh. Shkhanukov-Lafishev 《Computational Mathematics and Mathematical Physics》2008,48(10):1875-1884
Locally-one-dimensional difference schemes for the fractional diffusion equation in multidimensional domains are considered. Stability and convergence of locally one-dimensional schemes for this equation are proved. 相似文献
76.
Mapundi Banda Axel Klar Lorenzo Pareschi Mohammed Seaï d. 《Mathematics of Computation》2008,77(262):943-965
A relaxation system based on a Lattice-Boltzmann type discrete velocity model is considered in the low Mach number limit. A third order relaxation scheme is developed working uniformly for all ranges of the mean free path and Mach number. In the incompressible Navier-Stokes limit the scheme reduces to an explicit high order finite difference scheme for the incompressible Navier-Stokes equations based on nonoscillatory upwind discretization. Numerical results and comparisons with other approaches are presented for several test cases in one and two space dimensions.
77.
Göta Eriksson 《The Journal of Mathematical Behavior》2008,27(3):177-187
This article focuses on spontaneous knowledge-building in the field of “the arithmetic of the child.” The aim is to investigate the conceptual progress of fifteen children during their early school years in the compulsory school. The study is based on the epistemology of radical constructivism and the methodology of “multiple clinical interviews”. A model of “the arithmetic of the child” elucidates mental structures used by the child in solving problems. The individual interviews are video-recorded. The results show that the children's solutions are compatible with the model. When the researcher adapts problems to the children's available concepts to bring out their capability, they all solve them in their own ways. Further, the conceptual levels of the children differ to a great extent at school start and do not all show conceptual progress after 2 years of traditional teaching. An implication for an alternative teaching process is suggested, namely “the arithmetic for the child”, accomplished in a triadic teaching process. 相似文献
78.
在分析桩土支撑体系及其相互作用关系的基础上,利用有限元分析软件ANSYS建立了群桩
体系计算模型. 通过对均质土体例题计算结果分析,可以看出利用该建模方法与传统解答有
很好的一致性. 根据辽宁工程技术大学实验馆场地土实测资料,利用该建模方法,求解出了承台与桩的
荷载分担比,对安全、经济地进行群桩基础设计具有重要指导作用和应用价值. 相似文献
79.
C. Mansilha A. Melo H. Rebelo I.M.P.L.V.O. Ferreira O. Pinho V. Domingues C. Pinho P. Gameiro 《Journal of chromatography. A》2010,1217(43):6681-6691
A multi-residue methodology based on a solid phase extraction followed by gas chromatography–tandem mass spectrometry was developed for trace analysis of 32 compounds in water matrices, including estrogens and several pesticides from different chemical families, some of them with endocrine disrupting properties. Matrix standard calibration solutions were prepared by adding known amounts of the analytes to a residue-free sample to compensate matrix-induced chromatographic response enhancement observed for certain pesticides. Validation was done mainly according to the International Conference on Harmonisation recommendations, as well as some European and American validation guidelines with specifications for pesticides analysis and/or GC–MS methodology. As the assumption of homoscedasticity was not met for analytical data, weighted least squares linear regression procedure was applied as a simple and effective way to counteract the greater influence of the greater concentrations on the fitted regression line, improving accuracy at the lower end of the calibration curve. The method was considered validated for 31 compounds after consistent evaluation of the key analytical parameters: specificity, linearity, limit of detection and quantification, range, precision, accuracy, extraction efficiency, stability and robustness. 相似文献
80.
N. Villedieu T. Quintino M. Ricchiuto H. Deconinck 《Journal of computational physics》2011,230(11):4301-4315
We construct a third order multidimensional upwind residual distribution scheme for the system of the Navier–Stokes equations. The underlying approximation is obtained using standard P2 Lagrange finite elements. To discretise the inviscid component of the equations, each element is divided in sub-elements over which we compute a high order residual defined as the integral of the inviscid fluxes on the boundary of the sub-element. The residuals are distributed to the nodes of each sub-element in a multi-dimensional upwind way. To obtain a discretisation of the viscous terms consistent with this multi-dimensional upwind approach, we make use of a Petrov–Galerkin analogy. The analogy allows to find a family of test functions which can be used to obtain a weak approximation of the viscous terms. The performance of this high-order method is tested on flows with high and low Reynolds number. 相似文献