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-   -   Residuals problem (http://www.cfd-online.com/Forums/fluent/33637-residuals-problem.html)

steph May 4, 2004 03:05

Residuals problem
 
Hello everybody!!! I have a problem with the continuity's residual convergence.I use the k-epsilon realizable model and I have about 17000 cells. The calculation converges very well at the beginning of the calculation but just before the half of the calculation, the continuity's residual gets instable and doesn't converge. For information, the under-relaxation factor for pressure is 0.3 and 0.7 for the momentum.I have 200 time steps of 5e-4 seconds and 1000 iterations per time step. If anybody has an idea, he will be welcome. Thanks!!

bob May 4, 2004 03:12

Re: Residuals problem
 
I think you should try to reduce the under releaxation factor as per the manual.

steph May 4, 2004 03:18

Re: Residuals problem
 
0.2 for the pressure 0.5 for the momentum,k and epsilon?

bob May 4, 2004 06:21

Re: Residuals problem
 
yeah may be

Eric May 4, 2004 07:06

Re: Residuals problem
 
You should keep your pressure and momentum urf's equal to 1. So if pressure = 0.4 momentum = 0.6.

This was discussed in this forum sometime ago but I can't remember under what heading, sorry.

Eric

steph May 4, 2004 07:48

Re: Residuals problem
 
i think the sum should be 1.0 only for the SIMPLEC method as I understand in the FLUENT guide


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