In multiphase flow, each phase has its own velocity field, governed by conservation of momentum for the phase. In Eulerian-Eulerian multiphase flow, the full momentum equation is considered, including inertial effects of the phase. In some cases, however, if the time scales to reach the equilibrium slip velocity are small, it is appropriate to use simplified models for calculating the velocity of dispersed phases. This is the motivation behind the Algebraic Slip Model (ASM) for multiphase flow.