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Large residual distributed at uniform flow region |
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August 16, 2015, 23:10 |
Large residual distributed at uniform flow region
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#1 |
Senior Member
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15 |
As you can see in the attached pictures, the region with vortex doesn’t have large residual over there but the region with quite uniform flow is distributed with large residual which causes convergence problem. Could anyone explain that’s why and how to solve this problem?
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Best regards, Meimei |
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August 17, 2015, 02:54 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
You have very high aspect ratio elements in the wake region. It is always going to have a hard time resolving the wake when the elements are that long and skinny. You will need to reduce the aspect ratio of those elements.
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August 19, 2015, 00:45 |
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#3 |
Senior Member
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15 |
I improve the aspect ratio over there but convergence doesn’t become any better. I think coarsening the grids over the vortex region at the trailing edge is the general way to improve the convergence for this kind of problem (of course not too coarse).
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Best regards, Meimei |
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August 19, 2015, 01:31 |
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#4 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
Refining the mesh results in less numerical dissipation which means the inherent instabilities in shear layers, wakes and similar features become more difficult to resolve. So yes, I would expect convergence to get more difficult as mesh size gets smaller.
Be careful coarsening the grid as you will be loosing accuracy by doing it. Make sure it is not a critical part of the flow, and do a sensitivity analysis on it to be sure. |
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