Free surface - weir
 

I'm trying to numerically obtain the experimental results on flow in rectangular side weirs in straight open channel. Apart from the channel and side weir geometry(depth, width, height of weir crest) the only parameter I know is the Froude number and flow depth at just the beginning of the side weir.

At the inlet I tried velocity inlet with upstream flow depth and velocity corresponding to Froude number, volume fraction 1(water alone). However my flow depth reduces significantly by the time the flow reaches the weir.

Please tell me what I'm missing here. How to model the Froude number and flow depth together?

I used Eulerian multiphase, VOF model, gravity, k epsilon turbulence models.

Forgot to mention I'm simulating in star ccm+