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Cd or drag coeeficient converges and then diverges |
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August 31, 2015, 17:30
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Cd or drag coeeficient converges and then diverges
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#1 |
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New Member
vito
Join Date: Jun 2015
Posts: 22
Rep Power: 10  |
Hello All,
Please find below the plot for Cd for Flow past cylinder (RE=3900, RANS type SST k omega), it seems to stay steady for a while and then starts diverging and oscillating. My residual limits are low and I am PimpleFOAM as a solver. Has anyone experienced anythign like this before. Looking forward to some comments. |
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August 31, 2015, 18:24
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#2 |
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Senior Member
anonymous
Join Date: Aug 2014
Posts: 205
Rep Power: 12 |
As far as I am corcened, at that Reynolds number you should be obtaining an unsteady solution. Did you try to run your simulation for longer times? How is your mesh and y+?
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August 31, 2015, 18:28
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#3 |
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New Member
vito
Join Date: Jun 2015
Posts: 22
Rep Power: 10 |
Correction - Re= 3900 and I have a decent mesh or I belive..my Yplus obtaine dfrom Yplus RAS is less than 6 and I am not using any wall functions.
I have already run this simulation for about 60 seconds. I am sorry but when you say unsteady is it okj to assume that these fluctuations are normal i.e is it ok to see that divergence but again it is not about a mean value you see. |
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November 26, 2015, 13:43
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#4 |
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New Member
david caseiro
Join Date: Nov 2015
Location: Portugal
Posts: 3
Rep Power: 10 |
Your solution is not stable yet. You should have one solution like the one I have in attachment (forget about the cd because it's for another Re, but the development for your case will be similar)
So I would say: Let it go.... on. Continue the test. |
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