Optimizing core annular flow for heavy oil transport

Heavy oil transport in pipelines is limited by high viscosity, leading to large pressure losses and energy consumption. Core-annular flow (CAF), where oil is conveyed within a lubricating water layer, offers an effective alternative, yet its stability under gravity remains insufficiently quantified. This study numerically investigates the effects of gravity, oil density, flow velocity, and inlet water configuration on CAF stability using a Volume of Fluid (VOF) model coupled with the k– ε turbulence model and PISO algorithm. Gravity destabilizes CAF due to density stratification, as denser water migrates downward while lighter oil rises, deforming the oil core. Stable CAF was obtained at critical velocities of 2.0–1.0 m s −1 for oil densities of 854.8–960 kg m −3 . Optimizing the inlet water configuration reduced these velocities to 1.0–0.6 m s −1 and decreased pressure drop by 33%–50%. The results provide quantitative criteria for improving CAF stability and energy efficiency in heavy oil pipeline transport.