Problem in unstructured circular cylinder case
I'm trying to run the circular cylinder case for Re=3900 using unstructured grid (prism/tetras) generated by ICEM. I'm using a hybrid DES/LES model. Although I'm being able to run the case using Upwinding scheme, the solution blows off after some time as I switch to CD scheme. Does it have to do anything with the mesh quality, given the checkMesh output as:
Overall domain bounding box (0 0 0) (0.579999987 0.4199999906 0.07999999821)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (2.796323021e-17 1.133420052e-17 -2.412554847e-16) OK.
Max cell openness = 2.744236741e-16 OK.
Max aspect ratio = 5.985448358 OK.
Minumum face area = 1.860038895e-07. Maximum face area = 0.0001631631359. Face area magnitudes OK.
Min volume = 7.890352088e-11. Max volume = 7.346122294e-07. Total volume = 0.01946299762. Cell volumes OK.
Mesh non-orthogonality Max: 63.07437883 average: 7.798812186
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.8103598145 OK.
Are the parameters such as aspect ratio, skewness ok for OF to handle tetra domainated meshes?
Can someone advice any other settings (for schemes etc) which he/she would prefer for this case.
as I understand it unstructered grids increase the unboundedness of schemes.
I have had some succes using the blended scheme for the convection term, however, in my case (low-Re DNS) this gave so much numerical diffusion that the solution turned laminair (for 5 percent upwind).
You can also try to use really low CFL (<0.5).
Hope this helps.
Thanks for the reply. Can you please tell me how to use blending of Upwind and CD schemes in OF.
this is for 5 percent upwind:
div(phi,U) Gauss blended 0.95;
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