Under-relaxation factors
 

I know that a converged solution is independent of the value of URF's chosen. However, is it acceptable to change URF's in the middle of a solution and then continue iterating?

Re: Under-relaxation factors
 

Yes it is acceptable.

You're right when you say that a converged solution does not depend on the value of URF's, but the convergence of a solution is dependent on their values, and also by the combination of them.

Some authors like Peric, for example, suggests some rule of thumb like

a_velocity + a_pressure = 1

where a represents the URF.

Regards, ap

Re: Under-relaxation factors
 

regarding URF's,can excessive under-relaxation introduce accuracies in unsteady flows. that is, although solution will be converged but not accurate?

Swarup.

Re: Under-relaxation factors
 

Thanks Swarup, You meant "introduce inaccuracies" right?

Re: Under-relaxation factors
 

Thanks for the information ap. Very well worded indeed!