[snappyHexMesh] Layers collapsing when blockMesh used for overall refinement

snowylabrador · June 24, 2022, 12:00

I have a mesh with 15k cells and a layer around a blade, with extrusion for wall function turbulence model application, so ideally wouldn't want to change that layer thickness. I want to increase overall mesh refinement of the pump with the blades to check for mesh sensitivity, but as I increase the blockMesh dict refinement, the layers around the blade collapse as shown in the figure below.
Why does this happen, and what can I do to refine the overall mesh without this happening?
Thank you

AtoHM · June 26, 2022, 07:11

A) collapsing layers is a big problem with sHM, search this forum to find some recommendations, there are a lot
B) Your first cell height is ~1/4 of the blade thickness? I would strongly doubt that as a yplus requirement. Make sure you calculated it correctly.

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June 26, 2022, 07:11		#2
AtoHM Senior Member M Join Date: Dec 2017 Posts: 642 Rep Power: 12	A) collapsing layers is a big problem with sHM, search this forum to find some recommendations, there are a lot B) Your first cell height is ~1/4 of the blade thickness? I would strongly doubt that as a yplus requirement. Make sure you calculated it correctly.