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Applied Computational Fluid Dynamics Techniques - Wiley Episode 1 Part 3

Tham khảo tài liệu 'applied computational fluid dynamics techniques - wiley episode 1 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 36 APPLIED COMPUTATIONAL FLUID DYNAMICS TECHNIQUES Conforming Non-conforming Surface aligned Non-surface aligned Micro-structured Micro-unstructured Macro-unstructured Micro-structured Element type Figure 3.1. Characterization of different mesh types Element type describes the polyhedron used to discretize space. Typical element types include triangles and quads for 2-D domains and tetrahedra prisms and bricks for 3-D domains. In principle any of the four classifications can be combined randomly resulting in a very large number of possible grid types. However most of these combinations prove worthless. As an example consider an unstructured grid of tetrahedra that is not body conforming. There may be some cases where this grid optimally solves a problem but in most cases Cartesian hexahedral cells will lead to a much faster solver and a better suited solution. At present the main contenders for generality and ease of use in CFD are as follows. a Multiblock grids. These are conformal surface-aligned macro-unstructured micro structured grids consisting of quads or bricks. The boundaries between the individual micro-structured grids can either be conforming or non-conforming. The latter class of multiblock grids includes the possibility of overlapped micro-structured grids also known as Chimera grids Benek et al. 1985 Meakin and Suhs 1989 Dougherty and Kuan 1989 . b Adaptive Cartesian grids. These are non-conformal non-surface-aligned microunstructured grids consisting of quads or bricks. The geometry is simply placed into GRID GENERATION 37 an initial coarse Cartesian grid that is refined further until a proper resolution of the geometry is achieved Melton et al. 1993 Aftosmis et al. 2000 . The imposition of proper boundary conditions at the edges or faces that intersect the boundary is left to the field solver. c Unstructured uni-element grids. These are conformal surface-aligned microunstructured grids consisting of triangles or tetrahedra. Consider the task of .