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Under-relaxation (SIMPLE algorithm)

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Old   September 5, 2014, 05:11
Default Under-relaxation (SIMPLE algorithm)
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Mandeep Deka
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Hi everyone,

I am writing a finite volume based cfd code for simulating an incompressible flow through a pipe using the SIMPLE algorithm.
Should I implement under-relaxation of the pressure terms and velocity terms for this case?

Thank you
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Old   September 5, 2014, 09:14
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Troy Snyder
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Yes, the momentum equations require relaxation owing to the nonlinearity of the convective terms and SIMPLE's rough approximation for the velocity corrections requires relaxation of the pressure. Momentum relaxation is typically ~0.5-0.8 and pressure relaxation should be ~0.1-0.2. The specific values depend on the particular problem. Tuning the relaxation factors to prevent divergence but keep computational time modest is a trial-and-error process.
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