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Old   April 6, 2004, 09:03
Default Pressure correction
  #1
Ale
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Hi to all,

what kind of problem can lead to the following error message?

divergence detected in AMG solver: pressure correction

Thanks a lot in advance,

Ale
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Old   April 6, 2004, 11:08
Default Re: Pressure correction
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David
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Hi,

have you made sure you are using the right pressure discretisation scheme for your case?

David
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Old   April 6, 2004, 16:54
Default Re: Pressure correction
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ap
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You should give more information on the model you are using, anyway, first of all check settings of boundary conditions and of viscous model.

Hi

ap
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Old   April 7, 2004, 04:20
Default Re: Pressure correction
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Ale
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Hi, I am modelling non-premixed combustion in a 2D axisymmetric domain. I am solving for mixing and reaction by my own UDF code, and I let Fluent solve the fluid-dynamics (k-epsilon model).

I noticed that there are some convergence problems for continuity, momentum and turbulence, and sometimes I get the error on pressure correction.

I think that there should be a problem with my UDF (which determines density and temperature). Where do you think I should look for a mistake first? What kind of setting for pressure interpolation and pressure-velocity coupling should I use?

Thank you!

Best regards,

Ale
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Old   April 7, 2004, 08:27
Default Re: Pressure correction
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David
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Hi,

for pressure velocity coupling, SIMPLE is most generally fine and PISO is suitable for unsteady calculation as it accelerates the convergence.

It can also depend on what kind of mesh you are using (tetrahedral? hexahedral?) and whether the cells are aligned with the flow or not. If there is a swirling flow better use PRESTO or if strong body forces uses body weighted.

But convergence problems can come from different sources. Is your mesh fine enough where the pressure, velocity gradient are the most important? Are your boundary conditions settings sensible enough?

Look also at your under relaxation factors: if they are close to one, convergence will be accelerated but you can go into instability as well so you can increase them slighlty when you solution is converging. Use around 0.2 for pressure, 0.5 for momentum, kinetic energy and turbulence dissipation rate.

i hope this helps

David
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