Strange oscillatory pressure in periodic incompressible flow
 

Hello,

I'm trying to simulate a turbulent flow in a pipe-like geometry. The inlet boundary condition is periodic (velocity imposed) and the outlet BC is set to zero pressure. The pipe has sort of a ring/narrow section in the middle and among other things, I'm trying to plot the pressure difference between pressure values after and before the narrow part. I chose two cross-sections, averaged pressure in each of them and then took the difference. The result is the blue curve in the attached plot. Unfortunately, the pressure is quite oscillatory when the simulation is near inlet velocity peak and I don't manage to fix it. I tried to switch from second-order pressure to 'linear' and also to 'standard', but both only made the results look worse. Playing with relaxation parameters for pressure has some effect, but not sufficient for me to get a nicely looking result. Could you please advise what else could I change in the settings of the solver to remove the oscillations?

Thank you very much.

EmiS