Turbulent Poiseuille flow of two immiscible liquid layers inside a rectangular channel has been performed adopting a Direct Numerical Simulation of wall bounded flow, coupled with the Phase Field Model (PFM). A thin liquid layer flows on top of a thick liquid layer, their thickness ratio is h1 /h2 = 1/9. They have the same densities but different viscosities, which are: λ = ν1 /ν2: λ = 1, λ = 0.875 and λ = 0.75. The aim is to investigate the situation where water is used to transport oil in pipelines. The liquid-liquid interface produces remarkable turbulence modulation inside the channel compared to Single Phase (SP) flow.
From an economic perspective, the drag reduction effect is extremely interesting to pipeline operators. Adding a small amount of polymer can give significant advantages to transportation. However, challenges arise in dissolving the additives in high viscosity fluids such as heavy crude oils and in subsequent shear degradation. A thin layer of fluid added to the oil being transported through a pipeline can act as a lubricant, reducing pump pressure requirements.
Many researchers have studied the effects of viscosity and density differences on the dynamics of core-annular flow with two immiscible fluids. The first experimental results were reported by Clark in 1948. Later (1), he removed the buoyancy effect by matching the density of the heavy oil to the water density through adding a substance to the oil. Another experimental program (2) found that the two-phase oil-water flow rate increases with the addition of water in oil-water emulsions, compared to that of single-phase oil. In addition, the researchers observed a peak when the dispersed flow regime transited to stratified with mixing flow.