[flow_CH]

Hello

I am modeling a 3d open channel.
After convergence i want to find free surface height (Water height). I mean find bottom height of channel to free surface.
I am plotting density for air and water(mixture) in a defined line. But in plot results which density in closer to air i should choose for finding water height? (choosing (998) kg/m3 for water(in bottom of channel) and (......) kg/m3 for interface between water and air)
If you know other ways please say.

Thanks