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February 5, 2013, 10:52 |
Boundary Layer Low Re Turbulent Flow
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#1 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 15 |
Hi folks,
I'm implementing a Low Re k-ep model and, as mentioned in the forum on several occasions, I have to refine the mesh heavily near the wall. I have a boundary layer, and I have used the CFD tools for accessing the distance for the first layer. In my case it's 5E-6 m, which I think is very close to the numeric minimum value of the software. My question is this: as I refine the mesh near the wall, I get a problem in the convergence. The k and ep variables just stall at a certain residual value. Has anyone experienced this? Best Regards, Rui Silva |
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February 7, 2013, 01:36 |
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#2 |
New Member
Mohammed
Join Date: Feb 2013
Posts: 12
Rep Power: 13 |
Maybe you have reached convergence if stall at high residual value.
At what residual value it stalls before refining and after refining? |
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February 7, 2013, 08:30 |
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#3 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 15 |
Thank you for your reply Mohd123,
Before refining I get to about 10^-3 residual (standard for COMSOL) and after refining the value is about 10^-2. Could it be that the boundary layer mesh is to fine and causing numerical diffusion? Best Regards, Rui |
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February 8, 2013, 06:06 |
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#4 |
New Member
Mohammed
Join Date: Feb 2013
Posts: 12
Rep Power: 13 |
The best thing I suggest to do to make sure that mesh is totally independent of solution is to do a Grid Independence Study, so that you keep refining the mesh (from course to fine) until you reach a contant solution and the more you refine the mesh the solution will be constant.
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February 8, 2013, 06:28 |
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#5 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,893
Rep Power: 73 |
Quote:
for any consistent and stable discretization, in no way a grid refinement can cause an increasing in the numerical diffusion! Try check your iteration parameters |
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Tags |
boundary layer mesh, k-epsilon turbulence, low reynolds |
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