Influence of Pipeline Design and Flow Properties on Oil-Water Hydraulics: A Computational Fluid Dynamics Approach

Abstract Oil-water flow in pipelines is influenced by fluid velocity, inlet shape, oil viscosity, flow development length, pipe material, and interfacial tension. Conflicting findings in the experimental literature highlights the need for a deeper understanding of these variables. This study uses two-dimensional Computational Fluid Dynamics (CFD) simulations to explore the impact of these parameters on flow hydraulics. A reference simulation (base case) was established with parallel inlets, oil and water velocities of 0.45 m/s, oil viscosity of 0.025 Pa·s, interfacial tension of 0.36 N/m, and an entrance length-to-diameter ratio of 50. Key parameters were varied, including inlet shape, entrance length-to-diameter ratios, interfacial tension, and oil viscosity, velocity, and density. The Volume of Fluid model tracked interfacial dynamics, while the SST turbulence model simulated turbulent flow. The CFD model successfully reproduced the stratified flow with a mean absolute percentage error of 5.3% for the pressure drop compared to the experimental data. The input geometry significantly affected the pressure drops, with higher viscosity and velocity increasing the pressure drop, while shorter entrance length-to-diameter ratios caused incomplete flow development. The interfacial tension had minimal effect. This study offers insights into optimizing pipeline design and improving multiphase flow predictions in industrial settings.