NASA Technical Reports Server (NTRS) : Recent pdf

NASA Technical Reports Server (NTRS) : Recent

More Book Details

Description of the Book:

In the multidimensional CESE development, triangles and tetrahedra turn out to be the most natural building blocks for 2D and 3D spatial meshes. As such the CESE method is compatible with the simplest unstructured meshes and thus can be easily applied to solve problems with complex geometries. However, because the method uses space-time staggered stencils, solution decoupling may become a real nuisance in applications involving unstructured meshes. In this paper we will describe a simple and general remedy which, according to numerical experiments, has removed any possibility of solution decoupling. Moreover, in a real-world viscous flow simulation near a solid wall, one often encounters a case where a boundary with high curvature or sharp corner is surrounded by triangular/tetrahedral meshes of extremely high aspect ratio (up to 106). For such an extreme case, the spatial projection of a space-time compounded conservation element constructed using the original CESE design may become highly concave and thus its centroid (referred to as a spatial solution point) may lie far outside of the spatial projection.

It could even be embedded beyond a solid wall boundary and causes serious numerical difficulties. In this paper we will also present a new procedure for constructing conservation elements and solution elements which effectively overcomes the difficulties associated with the original design. Another difficulty issue which was addressed more recently is the wellknown fact that accuracy of gradient computations involving triangular/tetrahedral grids deteriorates rapidly as the aspect ratio of grid cells increases. The root cause of this difficulty was clearly identified and several remedies to overcome it were found through a rigorous mathematical analysis. However, because of the length of the current paper and the complexity of mathematics involved, this new work will be presented in another paper

• Creator/s: NASA Technical Reports Server (NTRS
• Date: 9/1/2013
• Year: 2013
• Book Topics/Themes: NASA Technical Reports Server (NTRS), SPACE-TIME CE/SE METHOD, THREE DIMENSIONAL MODELS, COMPUTATIONAL AEROACOUSTICS, NUMERICAL ANALYSIS, COMPUTATIONAL FLUID DYNAMICS, HIGH ASPECT RATIO, NAVIER-STOKES EQUATION, UNSTRUCTURED GRIDS (MATHEMATICS), PARTIAL DIFFERENTIAL EQUATIONS, VISCOUS FLOW, Chang, Sin-Chung, Chang, Chau-Lyan, Yen, Joseph C

An excerpt captured from the PDF book