Mesh with prism layer for 3D external flow

General
1

Hello, does anyone know how to create a mesh with prism layers that can be translated to pyfr mesh? I need to simulate flow past buildings. If only the ground prism layer (not on buildings) can be a great help.

I don’t think Gmsh is capable to create 3D prism layer at the moment (if someone knows how, please shed some light).

So I tried two other meshers - CFMesh+ and StarCCM+ then output cgns. But when importing cgns to pyfrm, i saw this error:

STAR-CCM - CGNS

ccm.png
ccm.png935×466 105 KB

CFMesh - CGNS
cfmesh.png
cfmesh.png908×249 61.2 KB

Seems the latter cgns mesh has some quality issue, but when i run checkMesh only found some high skewnesses and non-orthogonalities.

Thanks for reading!

Junting

2

Hi Junting,

You should be able to make a prism layer in gmsh by creating a triangular surface mesh on your object, and then using transfinite line/volume to stretch this outwards into a volume of prisms coming off of the surface. This is a bit difficult to explain here, but you can see an example prism/tet cylinder mesh in the supplementary material of the below paper that uses this approach:

https://www.sciencedirect.com/science/article/pii/S0045793015002509

Also, regarding your error importing the mesh I think it is mostly likely one of two things:

  1. You are missing boundary condition information of the surface faces of your domain
  2. You mesh is broken and some internal faces are not paired to each other

Hopefully that helps,

3

Hello Brian, I don’t think the method you use to create prism layers on the infinite length cylinder works if the object has an end.

I am not very familiar with CGNS and its library. I will look into that. All I have been doing so far was outputing the mesh to cgns format (hdf5) directly from the mesher. I did define boundary conditions in the mesher though, and the cgns format can be loaded with ParaView 5.7.

Junting Chen