Inertial effects in triple-layer core-annular pipeline flow

Abstract

Triple-layer core-annular flow is a novel methodology for efficient heavy oil transportation. As usual, high shear rates concentrating in a lubricating fluid layer reduce the pressure drop significantly. Novel is the use of a viscoplastic fluid bounding the lubricant and protecting the transported core. For sufficiently large yield stress, the skin remains unyielded, preventing any interfacial instabilities. By shaping the skin, we generate lubrication forces to counterbalance buoyancy of the core fluid, i.e., an eccentric position of the core is the result of buoyancy and lubrication forces balancing. Here, we extend the feasibility of this method to large pipes and higher flow rates by considering the effects of inertia and turbulence in the lubrication layer. We show that the method can generate enough lubrication force to balance the buoyancy force for a wide range of density differences and pipe sizes if the proper shape is imposed on the unyielded skin.