# UNDER-RELAXTATION FACTORS??????????????????

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 March 22, 2006, 04:21 UNDER-RELAXTATION FACTORS?????????????????? #1 Anne Guest   Posts: n/a Sponsored Links Hello hello everyone. what is the less UNDER-RELAXTATION FACTORS, to put in solution controls. is there a rule to respect?????????????? thanks.

 March 22, 2006, 09:40 Re: UNDER-RELAXTATION FACTORS?????????????????? #2 Nick Guest   Posts: n/a not really , all you are changing is the ratio of values for subsequent interations. The minimum values I tend to put in are of the order of 0.01 , say my solution is blowing up due to temperature I will reduce the energy to that kind of value and maybe back it off a bit when the solution has calmed down. Obviously the lower the value the slower your solution will take to converge !

 March 24, 2006, 10:03 Re: UNDER-RELAXTATION FACTORS?????????????????? #3 sean Guest   Posts: n/a Hi Nick, so we can lower the under relaxation factors of all governing equations to such a low value ? In the manual they suggest to reduce, eventually, to about 0.8 the energy equation, 0.2 pressure, 0.5 momentum, k and epsilon. Thanks for you help, Best Regards.

 March 24, 2006, 10:10 Re: UNDER-RELAXTATION FACTORS?????????????????? #4 Nick Guest   Posts: n/a yes, I regularly reduce these numbers to such small values, I can't say that I have gone beyond this though. One thing to remeber is that you can do, is to increase the underelaxtion ! Say for example that you have a very stable solution you could well up the pressure to 0.4 or so to speed up the convergence, but this will be very model dependant.

 March 24, 2006, 12:56 Re: UNDER-RELAXTATION FACTORS?????????????????? #5 sean Guest   Posts: n/a ok, thanks a lot! but, will the solution be affected by choosing so low values of URF? Regards.

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