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-   -   urgent help for under relaxation parameters (http://www.cfd-online.com/Forums/fluent/79274-urgent-help-under-relaxation-parameters.html)

Mansureh August 18, 2010 11:40

urgent help for under relaxation parameters
 
Hi everybody
How can I change under relaxation parameters to get converged solution when I simulate a multiple reference frames(MRF) case and residuals fluctuate. I mean which parameter should be changed and how much?

thanks for any help

xrs333 August 18, 2010 12:04

Hi, Mansureh,
If the calculation is diverging, reducing under relaxation may alleviate the the problem, but may impede the converging speed. And the reason underlies is you incorrect building of the model or initial values for iteration. So, my advice is better model and better initial values. And now that you are using MRF, use solution strategies for MRF.

Mansureh August 18, 2010 13:35

Need more help
 
Dear friend, xrs333
Thanks very much for replying. could you tell me how can I find information about MRF strategies,please? can I find it in Fluent help documents? let me explain more about my geometry. It consists of several coaxial annuluses that two of interior ones rotate in relatively high rotational speed. gas flow inters from the outermost annulus and exits from the innermost one. I want to obtain gas pressure drop from the inlet to outlet, but the result is lower than that must be. I use RNG k-epsilon turbulence model. could you help me about this?

thanks


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