[quarkz]

Hi,

I'm reading the presentation by Wolf dynamics on controlling the transition
from the boundary layer mesh to the far field mesh.

In the attached picture, the right one is better than the left. However, it is not explained what changes have been done to achieve it. Can some experts help?

Thanks.

[AtoHM]

To me it looks like more layers and possibly a slightly higher ratio on the right. Regarding the topic name: you can specify several combinations of layer parameters. E.g. the first layer thickness and ratio, or the overall thickness and ratio (and nLayers of course). To influence the transition to the background mesh, you can specify a combination with the final layer thickess.


What combinations are valid will be printed out when u overload the definition, e.g. provide first and final layer thickness and ratio. Then you get a printout of the accepted combinations.

[quarkz]

Thanks for the suggestions AtoHM.

Yes, there are slightly more layers on the right. I know how to specify the layers and their thickness. However, I'm more concerned with the transition from small quads to the triangles and then the bigger quads.

In my simulation, I have the "smearing gradients" as described by wolf dynamics. I hope to have more small quads in the wall vicinity before they transition to triangles and large quads.

I'm guessing that it has something to do with mode distance and levels. However, I haven't been able to get it right.

[Yann]

Hello,

You can change the nCellsBetweenLevels parameter to add more cells between each cell level transition. Your left pic looks like nCellBetweenLevels = 2.
https://doc.openfoam.com/2306/tools/...sBetweenLevels

This will change the number cells at each level transition, so it can increase a lot the cell count if you have a wide range of refinement levels in your mesh.

To explicitly control the cell sizes and transitions around your object you can use the distance mode in the refinementRegions section : https://doc.openfoam.com/2306/tools/...inementRegions

[quarkz]

Hi Yann,

Thanks for the suggestions. I tried the distance mode but it doesn't seem to work. I'll try with different settings to see if it works. Will post here if there's improvement.

[quarkz]

Hi, I found that the nCellsBetweenLevels parameter is the main factor controllling the change, as mentioned by Yann. Hope that helps!