boundary conditions in twoPhaseEulerFoam
 

I am trying to solve multiphase problem and I used twoPhaseEulerFoam
The problem is like below.

phase A : air(discontinuous)
phase B : liquid(continuous)
density : A<<B

system : initially filled with phase B, gravity=(0,0,-9.8)

inlet : alpha A=0.1, Ua=(0,0,-10), Ub=(0,0,-10)
outlet : pressure outlet(p=0), back flow could be happened.

At that case, how should I set the boundary conditions for alpha, U1, U2, p, etcs?