Three dimensional simulation of flow development of triple-layer lubricated pipeline transport

Abstract

In heavy oil pipelining, a major challenge is to reliably achieve high rates of pressure drop reduction in stable annular flow patterns. Sarmadi et al. (2017), introduced a novel methodology for efficient transportation of heavy oil via a triple-layer core-annular flow. The lubricating outer layer is separated from the core by a shaped skin comprising a yield stress fluid. The lubricant reduces the pressure drop, the unyielded skin eliminates interfacial instabilities and the shaped interface produces lift force in the lubrication layer to balance buoyancy of the core. Sarmadi et al. (2018), studied how to sculpt the interface in stable controlled way and how to establish the flow. Here we present three dimensional (3D) triple-layer computations which capture the buoyant motion of the core to reach its equilibrium position. The 3D computations are performed using a finite element method and adaptively aligned meshes to track dynamically the interfaces, benchmarked against axisymmetric computations from Sarmadi et al. (2018). The study shows that these flows may stably become established with control over interface shape, but development lengths (times) for the core to attain equilibrium are relatively long, meaning extensive 3D computation. We also present a simplified analytical model using the lubrication approximation and equations of motion for the lubricant and skin layers. This model allows us to quickly estimate motion to the balanced configuration for a given shape and initial conditions.