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Old   June 1, 2005, 13:28
Default Under-relaxation Factors
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Hi everybody

I am analysing a flow over a special geometric body. i find ridiculous values of drag coefficient.

When i change the momentum value of under relaxation factor to half, drag coefficient changes

What do i expect from changing under relaxation factor?

Is it safe to change them in order to get the expected results?

Thank you
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Old   June 1, 2005, 14:10
Default Re: Under-relaxation Factors
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Judge your convergence by monitoring the drag coefficient at a specific point/surface in your domain. If your flow is steady, then wait for the monitor to level off or exhibit steady fluctuations about a steady value. That will indicate convergence. Theoretically, converged results are independent of the Under Relaxation Factors chosen.
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Old   June 1, 2005, 15:10
Default Re: Under-relaxation Factors
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To expand the problem, i can say that i already know the drag coefficient value of the shape from the literature. The value that fluent gives me is different (applying the standart procedure of aerodynamic analysis).

I think you meant the drag coefficient should not change with the und. rel. fac. ,but it does...I came across satisfying result with some under rel. factors with manually changing (the momentum value).

Thanks for answering by the way.

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Old   June 1, 2005, 19:11
Default Re: Under-relaxation Factors
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You may reduce the tolerance for the residuals by 10 or 100 times to get better results.

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