How can I solve at the interface region
 

Hi all: I have stratified two phase (air-water) flow into a pipe I am use the VOF model . I want to solve my problem at the interface region along the axial direction only such that I am not interested with the y-direction so is that possible ? Can anyone kindly tell me how can I did that with clear details? Knowing I am treating with unsteady state?

Thanks K. Baker