p_rgh wall boundary condition in interFoam
 

I am using interFoam to simulate air flow injected into tayler couette flow. I tried zeroGradient and buoyantPressure on the wall boundary. The code crashed after running several minutes. Then I used the fixedFluxPressure as in the capillaryRising case. The simulation runs steady and results are fine. Since the flux on the wall is zero, is the pressure gradient is also supposed to be zero. Is there any particular reason to use fixedFluxPressure boundary condition?

Thanks