[Mandeep Deka]

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

[tas38]

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.