Hello hello everyone. what is the less UNDER-RELAXTATION FACTORS, to put in solution controls. is there a rule to respect?????????????? thanks.

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 !

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.

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.

ok, thanks a lot!

but, will the solution be affected by choosing so low values of URF?

Regards.