Thank you. I could try pressure outlet boundary condition then I guess. In the Ansys forum discussion that you attached, I have a question. I am not sure where to ask the question here or there. I am posting here, please let me know if I have to move my post to the other thread. nThe back flow fraction = 0 , means only one phase is let back in and that's what the answer is mentioned as, but still I am confused. Does this mean, phase 2 is let out and only phase 1 is allowed to come back in ? when back flow fraction = 1, then both phase 1 and phase 2 is allowed to come back in ?.Regards,nKailash R.n