Custom Boundary Condition

What is the difference between pressure inlet velocity and pressure inlet-outlet velocity in the custom boundary condition in CFD? When would you use each?

Hi @dunnoebruh. I know what such B.C’s do in OpenFOAM, but I am not 100% sure for SimScale. So I will leave some question marks if I am not sure:

Pressure inlet-outlet velocity:

  • If the flow leaves the domain, treats it as a zero-gradient.
  • If backflow is present (flow into the domain), sets a predefined velocity. I see no such option in SimScale, so I suppose it is set to 0 to avoid backflow, right???
  • Applicable to vector fields (i:e: Velocity field):
  • Useful as an outlet for highly unstable flows where backflow is possible.

Pressure inlet - velocity:Pressure Inlet and Outlet | Boundary Conditions | SimScale tells you what it does:

  • It is an inlet B.C.
  • It is used when you know the inlet pressure (but not the velocity) or when you are setting the velocity at the outlet. But how is the ref. pressure set???
  • In theory you should be able of setting a reference pressure value but this is not the case.