Mechanistic modeling of critical sand deposition velocity in gas-liquid stratified flow

Abstract

Among the different regimes in multiphase pipelines, stratified flow is most prone to sand deposition, owing to the low liquid velocity and the lack of mixing. The main goal of this study is to predict the critical sand deposition velocity under stratified flow. The critical sand deposition velocity is defined as the minimum velocity that keeps all particles moving at all time, above which there is no stationary bed at all.Two models with similar approaches are developed based on the forces acting on a particle, such as the drag, turbulent, apparent gravity, van der Waals and lift forces for prediction of the transitions between moving/stationary dunes and moving/stationary bed. Dune pilling up and collapsing mechanism considering a torque balance on a rolling particle located at the top of the dune is adopted for stationary dunes. Torque balance applied to a rolling particle located on the lowest stratum of the moving bed layer is used to predict the minimum liquid film velocity for particle to grow a stationary bed. Comparison between the predictions of the two mechanistic models and the experimental data show good agreement, with critical sand deposition velocity absolute relative errors at 16.4% for stationary dunes and 12.6% for stationary bed.