[quarkz]

Hi, I'm trying to run LES simulation. In the article by Wolf dynamics on "Turbulence modeling in OpenFOAM - Theory and applications", it is stated that the recommended mesh near wall should have delta x+ and z+ < 4*y+ for LES simulation.

As shown in the diagram, the x+ ~ 10*y+. What are the key variables which I must change in snappyHexMeshDict in order to achieve it?

Can someone help?

Thanks.

[AtoHM]

Disclaimer: snappyHexMesh is not a great tool for accurate low-Re meshes. If you look around here, alot of topics are about creating good layers but most of the time, its not possible to get a good solution.


That being said, you got to estimate the yplus, e.g. with this tool https://www.cfd-online.com/Tools/yplus.php. Then in the snappyHexMeshDict in the addLayersControls you set

relativeSizes false;
expansionRatio <whatYouWish>;
firstLayerThickness <yourValue>;
minThickness <smallerThanYourValue>;

layers
{
    YourMeshRegion { nSurfaceLayers <nLayers>; }
}

Where firstLayerThickness is what the yPlusEstimator puts out. minThickness should be below, about 1 or 2 magnitudes to allow the layers growing in all regions.
Good luck!

[quarkz]

Hi AtoHM, thanks for the reply. I have already set the firstLayerThickness and expansionRatio. I'll check out the minThickness option.