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novice November 22, 2005 23:58

under relaxation factor

I am running a transient analysis with free surface. My run is diverging after some time, so I have reduced the time step. But this has very less effect on divergence. When I reduced the 'under relaxation factor for pressure correction' the run is running fine. But after some time it again diverged. So I reduced it further. So I just want to know how low I can go there? WHat is the effect. Thanks all

DB November 26, 2005 02:10

Re: under relaxation factor
Normally under-relaxation factor should be between 0.8-1.0


zxaar November 28, 2005 05:18

Re: under relaxation factor
If you case the convergence is difficult, then you could decrease the urf for pressure to 0.1 from default of (i think 0.3), and increase the urf of mom to 0.8 to 0.85. Further increase the pre and post iteration in AMG solver settings, this will keep the solver stable. If it does not help then check the skew of the mesh, the unstablity is due to this (most probably)

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