Boundary conditions for 3D multiphase simulation
 

Hi! I wish to simulate a 3D multiphase tank, In which i am stuck up while setting up the boundary conditions.
I have
1. Model's inlet velocity, inlet volume fraction (93% & 7%) of two fluids.
2. Model's outlet flow rate in each of the outlets.

I am using 'mixture' model.

So, i have decided to use 'velocity inlet' for inlet boundary condition.
But i am stuck up with outlet boundary condition.
Can you help me? also, please suggest me, any other model will be better for the boundary conditions, i have.