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How to make a good Low-Re Mesh ?

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Old   February 12, 2010, 05:48
Default How to make a good Low-Re Mesh ?
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Jérémy Bulle
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Hello,

I've read the wiki about general tips to make a good low-re mesh but it seems I still have problem with mine since openfoam gives weird result and our professor told us that the problem is probably the mesh (speed seems ok but pressure does not converge)

My geometry is similar to a pipe with the dimensions :
Hydraulic diameter : 0.08m
Length : 0.8m

So i would like to know :

- How can you know the size of the boundary layer approximately? How do you mesh it?
To make it simple I have a straight 2D-Path, so it has 2 walls. What I did is cut it in three parts : 2 near the wall for the boundary layer, one for the central path.
I mesh the two sides path with a 0.0001 interval length and no grading (0.0001 is it good? How can I know since y+ tools given in the wiki to estimate the first cell place gives me values about 0.000001 wich are VERY small to me ...)

I mesh the central path beginning with 0.001 and going to 0.01 to not have an abrupt change of the cell size.

For the perpendicular meshing to the boundary layer mesh I mesh with a no grading 0.01 interval length.

Can you tell me if it seems ok or where I could be wrong?

Thank you very much for the help!
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