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P-Mass residual convergers very quickly

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Old   October 18, 2005, 06:53
Default P-Mass residual convergers very quickly
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M
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Hi all, I am currently running a simulation with aoir flow throiugh a duct work with bends and curves. It has 1 inlet with a mass flow boundary condition and 16 openings with pressure conditions. When i run the case the mom residuals and the turbulence residulas converge as expected but the P mass residual starts off at a very low value and converges within 1 itteration to below 1.0e-06. This seems odd to me? I have checked the geometry and the results and they seem fine. Would anyone know why this is happening?

Thanks,

M
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Old   October 18, 2005, 08:36
Default Re: P-Mass residual convergers very quickly
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Robin
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This isn't a surprise. The solver is strongly conservative and it is quite normal for the mass residual to drop to round-off very quickly for simple, incompressible flow simulations.

-Robin
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Old   October 18, 2005, 23:56
Default Re: P-Mass residual convergers very quickly
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Bak_Flow
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Hi,

this sounds like a scaling issue. The standard residual (which has dimensions of Coeff * variable) is normalized by the largest coefficient and the range of variable in the domain. Sometimes this can go wrong. Make sure you monitor some integral quantities just to be sure it is converged!

Or maybe it is magic.....as the CFX sales guys would like to say the solver is just that good! ;-) You are better off questioning things yourself!

Regards,

Bak_Flow

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