# low Re on unstructured triangles

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 April 1, 2004, 06:49 low Re on unstructured triangles #1 dominik Guest   Posts: n/a hi, does anyone has experience with solving creeping flow on unstructured triangular mesh with variables in CV centers? my question is: on a grid of reasonable quality (yet not perfect) - is it enough to take cell face centers values as avergage (ev. more clever weighted than 0.5) of corresponding CV centers values? is it enough for not neccesarily very accurate but *stable* calculation? proper 2nd order would be a lot of geometrical calculations... (intersections, distances etc.) regards dominik

 April 14, 2004, 22:43 Re: low Re on unstructured triangles #2 Chris Guest   Posts: n/a Really the *stability* of a calculation depends on the behavior of the equations being solved. Fortunately creeping flow are diffusion dominant and the equations (I assuming Navier-Stokes) behave elliptically. By averaging the face-centers (using neighbouring cells) and using those face-centers to construct your cell-centered solutions -- this would be a central difference scheme, which is of course 2nd order accurate. Central difference schemes are unstable for hyperbolic equations because the information propagates predominantly in a single direction ... but since creeping flows behave elliptically, ie information spreads in *all* directions, a central difference *should* work.

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