convergence problems using simpleFoam
Hi,
I'm trying to simulate a dust enclosure. The first I want to simulate is the closed enclosure. I have one outlet (with a given velocity of about 20 m/s) and 2 or 3 inlets (with a given pressure of 0 Pa). Later I want to simulate with open door (pressure 0 Pa), to look if there is an outflow. For this I had made a model in *.stl. I meshed this model using snappyHexMesh. Now I have the problem, that the solution does not converge. Sometimes it blows up, and sometimes the residuals stay at one point and go up and down slowly (many iterations). So I can't get a right solution. I also viewed the results in paraview, but I can't see a steady solution. For example: Code:
Time = 815 Code:
Mesh stats Code:
RASModell laminar Code:
p Code:
div(phi,U) Gauss upwind; Code:
U I hope you can help me with this problem and give me an hint to clear the fault I surely made somewhere. If I should give you further informations don't hesitate to ask. Thank you very much. Sebastian |
Hi
your skewness is very bad (3.8), best results coming from having it below 0.9. you could also try leastSquares (or faceLimited) as gradSchemes and maybe gammaV 0.2 for div(phi,U). and upwind for the turbulence properties. I would still focus on the grid skewness as my main place of interest. Try using another mesh generator like Netgen, Engrid or Salome. Code:
ddtSchemes Code:
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Hi again
another thing if you have it write out values often you can open paraview and examine where the solution values blow up. This way you can examine the mesh where this occurs and I bet it is where you have your most skewed cells. I once had one badly skewed cell (4.12) and it made the whole solution crash. So even though checkMesh states the mesh is ok you have to use your common sense to see if "you" accept it to be ok :-). |
Yes you're right, I saw this phenomenon before, that two skewed cells at the inlet make trouble. I refinde the mesh using snappyHexMesh with refinementRegion or sth. like that. The mesh I had bevor was even worse than this.
I decided to use sHM cause, the other tools often crash (netgen) or do something for long time without feedback (Salome). But I think I have no other chance and so I'll give Salome a second chance and try it. The schemes you told me, I will try them tomorrow (probably on the new mesh). Thank you for your help |
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