I am trying to model flow through an open channel with a submerged pressure inlet. The situation is in a river so the inlet pressure is constant and the outlet river level is known and constant. I set up the implicit VOF model and define the input pressure but the downstream water level never rises above the height of the inlet. I want the water to be 3m deep with a 1m high inlet fully submerged injecting water to the channel.

Any ideas about what to do next? Am I using the correct model and am I on the right track?

Thanks in advance

This class of problems is normally solved by using a mass flow inlet and a hydrostatic outlet pressure bc. As a hydrostatic pressure field will develop your bcs need to accommodate this.