Weird velocities in multiphase flow

Richard

Hi, hope someone can explain this... I'm trying to model water waves and have so far got a good free surface profile. Unfortunately the velocity vector field looks very strange, with vectors emanating from the surface at hundreds of metres per second, and fluid apparently going straight down through the floor. This is with the default setting of superficial velocity turned on under "porous formulation".

When I run the solver using physical velocity instead, the resulting vector field looks great, but now the free surface profile is wrong - it shows the wave amplitude decaying with distance.

Can anyone shed some light on this phenomenon? I haven't specified a porous medium anywhere in my model, so surely superficial and physical velocities should give the same results? Any ideas appreciated.

Thanks, Richard