Mass Flow Inlet and
 

I am going to model an open channel flow with water and air in a 3D model in Fluent. Can anybody recommmend some tutorials for this?

The inlet area is 1.25 m^2 (1.25m x 1m) and I want it to be half filled with water. The model was initialized with air and then patched half full with water. Mass flow inlet was chosen with a flow rate for water 62.5kg/s (A*rho*v = 0.625*1000*0.1) and for air 0.77 (0.625*1.225*0.1). The outlet boundary was set to outflow with a flow rate weight of 1.

The results show a wave like motion where the water level is higher at the outlet boundary than at the inlet. Why could this be? Any comments on the setup of boundary conditions? Or could it be another explanation?

use VOF multiphase model, its good for free surface flows. You do have Tutorials, download from ansys website.