[adam96]

I am running an open channel flow case in OpenFoam (using interfoam). It is a simple two-phase (water and air) flow over a bump (image below).

Given that the flow is subcrtical at the inlet and supercritical at the output I expect the height of the flow to decrease over the bump and remain the same thereafter. But I am getting different results. Is there a problem with these boundary conditions:

Volume Fraction : zero gradient inlet and outlet.
Velocity: Fixed value inlet and zero gradient outlet

Pressure: zero gradient inlet and fixed value (p_rgh =0) pressure outlet.