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 Tony Tonton February 17, 2000 21:55

Grid

Hi! Can any one can tell me what is the difference between structred grid and unstructured grid. That is,what is a structured grid. thanking you in advance

Tony

 Burley Wang February 17, 2000 23:43

Re: Grid

I've asked the same question at sci.physics.computational.fluid-dynamics

here is the answer posted by Bob. Thanks Bob.

***************** Very briefly there are mainly two types of grids, structured and unstructured (defined below - and we needn't really discuss chimera grids or other such constructs). Although CFD largely uses the former and structural mechanics the latter, there are now many CFD applications which use unstructured grids. A major difference between unstructured grids for CFD and those for structural mechanics arises largely from the differences in the phenomena being modeled by the respective sets of equations. For many structures, a rather coarse grain structure is needed, whereas for CFD, fine structure is almost always needed somewhere.

structured grid - one where there is a regularized numbering pattern corresponding to cell position. Typically this means that a numbering scheme based on grid indices is sufficient to determining the neighbors of a given cell. For instance, the 2D cell whose indices are (i,j) always has four neighbors (i+1,j), (i-1,j), (i,j+1), and (I,J-1). The only exception being at boundaries.

unstructured grid - one where there is no generally definable pattern for determining the neighbors of a given cell. Thus lists of cell neighbors must be kept. This sounds like a big disadvantage, and it is, but one big advantage the unstructured grids have over structured is that they can be generated extremely quickly and can easily pack cells into high gradient regions whereas this takes some effort for the structured grids.

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