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Old   July 7, 2016, 13:45
Default Problem with incompressible flow
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I have a simple tube, which I am trying to benchmark a Poseuille flow with it. I have zero pressure gradient and some mass flow in inlet and a prescribed pressure at the outlet, and no slip at the walls. I measure the pressure at the inlet and I can compare that with analytical solution. When I use compressible flow there is no problem but when I use the incompressible flow the time steps drops to the minimum time step (1e-16s) and the pressures go crazy. Is there any problem with incompressible solver or I am missing something.
Thanks for your help.
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Old   July 11, 2016, 16:55
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Allie Le Moine
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Hi amrrhm,

When you switched from the Compressible to Incompressible solver did you make sure to load all of the default settings?

If pressure is not converging, one thing you can do is change the pressure solver type from SOR to BiCGSTAB (Under Simulation Parameters > Solver parameters > Equations > Pressure > Solver type). BiCGSTAB is a Krylov method which is known to perform well for incompressible flows. For more information on the Biconjugate gradient stabilized method please see the Theory Manual.

Thank you,
Allie Le Moine
Research Engineer | Applications
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Old   July 12, 2016, 09:18
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Thanks Allie,

I could make it work for simple geometry by increasing the maximum number of iterations in pressure equation, but for complicated geometry it is still not working.

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incompressible flow, poiseuille flow

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