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swati_mohanty June 11, 2009 00:01

Low under relaxation factor
Dear all,
i am running a VOF model for air water system and find that the residuals for the continuity equation do not converge using default under relaxation factors. I have changed the under relaxation factor for momentum to 0.01 and find that the convergence is much better. However, is it advisable to use such a low URF.

Thanx in advance


Piotrek June 11, 2009 08:13

dear swati,

By lowerign URF to such a low value, you limit any chance for the results to change. It makes in difficlut to estimate if the results are changing and you need considerable number of iteration to pass in order to see any influence.
I suggest lowering UDF gradually. Starting from default value and lowering by about 10-20% once the residuals are stable - not changing.

If you see no change in relevant variables on chosen surface, after a number of iterations you can judge, that the run is converged.

Hope that helps/

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