An optimized CFD-DEM method for particle collision and retention analysis of two-phase flow in a reduced-diameter pipe

High-concentration solid-liquid two-phase flow causes particle erosion or accumulation at the sudden change positions of flow channels, resulting in pipe leakage and tool failure. In existing CFD-DEM methods, since the particle time sub steps cannot be infinitely small, local high-speed particles may penetrate each other. In the current study, the CFD-DEM method is optimized by adding the judgment condition of particle collision forces so that the DEM can automatically reduce and restore the particle time sub steps to obtain a precise solution, which avoids the penetration caused by the high-speed collision of particles. The fracturing fluid and quartz particles were used to conduct sedimentation experiments to verify the simulation results. The research on the two-phase flow in the reduced-diameter pipe that the newly proposed simulation model could predict the distribution, retention, and erosion of the dense high-speed particles, whose movement mechanism in high-speed two-phase flow have been logically explained.