Numerical analyses of the solid particle erosion in elbows for annular flow

• The complex annular flow is converted to single-phase flow based on mechanistic analyses.
• The cushion effect of liquid film is indirectly simulated through correlations of the film thickness.
• The procedure is simple and efficient by providing rational treatments for erosion predictions.
• The simplified annular flow simulation and the erosion prediction are validated.

Solid particle erosion in pipelines is a severe problem involved in hydrocarbon transportation and hence an important topic in flow assurance. A simplified CFD-based procedure is proposed to calculate the penetration rates in elbows for annular flow. This new method overcomes the disadvantages of current empirical or semi-empirical models. The procedure consists of three main sections: flow modeling, particle tracking, and penetration calculation. The k–ε model is employed to analyze the flow field in the core area of the pipe based on the assumption that the gas–liquid interface is regarded as an actual pipe wall. Then a Lagrangian method is adopted to track trajectories of the entrained droplets and sand particles in the core area, and the velocity decay of sand particles across the liquid film is calculated combined with the film thickness correlation. Based on the knowledge of the flow field and the particle motion, penetration rates are calculated by introducing the solid particle erosion equation. By comparing with experimental data available from the literature, the new method is proved to be reasonable in simplifying the simulation of annular flow field and shows good accuracy in erosion prediction. A better agreement between predicted erosion rates and experimental data can be made when applied to larger curvature radius elbows.