Numerical study of stratified oil-water two phase flow in horizontal and slightly inclined pipes

In the present study, the stratified oil-water two phase flow is numerically simulated using multiphase Volume of Fluid model. The effect of flow parameters such as input velocity, material parameters like viscosity and density and geometric parameters such as diameter of pipe, orientation of pipe with the horizontal in the downhill and uphill inclination on velocity distribution and hold-up was studied. The model was first validated for oil-water stratified flow with the available experimental studies. The results showed good agreement with the available experimental and numerical results. The model was used to simulate the oil-water stratified two phase flow in a three dimensional pipe assuming that local slip is absent, there is no foaming at the interface, a uniform flow enters the domain. The volume of fluid model for multiphase was used, standard k-epsilon model was used for turbulence, pressure - velocity coupling was achieved by SIMPLEC algorithm.;In the case of uphill flows it is observed that, inclination affects the velocity profiles and oil phase has more velocity. The velocity magnitude of oil phase increased with angle of inclination and the percentage increment is observed to be greatest at low input velocities. The increase of input velocity showed that the velocity profile was more symmetric about the centerline. The slip velocity was more in pipes of large diameter as compared to that in small diameter pipes. The effect of viscosity nullified the effect of small uphill inclination angles. A density ratio much less than 1 lead to more slip velocity between the phases. In the case of downhill, flows, the effect of inclination was to increase the velocity of water phase. The magnitude of increment was more in case of downhill flow cases as compared to uphill cases. The size of pipe affected the velocity profiles with pipes of large diameter having more slip velocity. The effect of increased velocity input showed that the asymmetric nature of velocity profile is not completely lost in downhill flows. At high viscosity ratio, there was an instant increment in velocity of phases in the entry region and there by decreased downstream.