 we are working with multiphase flow in small middle ( cylindrical) section  of liquid-liquid extractor. Our primary purpose is to analyse flow pattern of  countercurrently  flowing two liquids.Now in this case, is it possible to define two boundary conditions on a single surface ? ( I want to define inlet of high density liquid and outlet of light liquid on upper end and inlet of light liquid and outlet of  high density  liquid on lower end.)
