<p>When using the unresolved CFD–DEM (computational fluid dynamics and discrete element method) method to simulate two-phase flow problems of sand carrying in wellbore, the process of sand particle collision and deposition can be described from a mesoscopic perspective, but there is a contradiction between computational efficiency and computational accuracy. The traditional CFD–DEM method solves the two-phase flow by time incremental way. Setting the fluid solution time step as an integral multiple of the particle time sub-step can solve the problem of the accuracy of particle domain solution or efficiency of the fluid domain solution to a certain extent, but it will still lead to the low efficiency of fluid domain calculation or rough description of flow field details. The novel iterative convergence criterion and time advancement algorithm of fluid solid coupling are established by improving the solution strategy of unsolved CFD–DEM in terms of particle drag force by fluid. By introducing the velocity judgment threshold, the force acting on particles is updated for the calculation of the next DEM time sub-step when the relative velocity between fluid and particles is larger than the threshold and there is no need to update the force between the fluid and the particle at each particle time sub-step. If it is less than the given threshold, the force information of the particles at the previous position is used, which improves the calculation efficiency and ensures the calculation accuracy at the same time. After each DEM time step, the particle swarm domain information will be updated through extracting flow field information at the corresponding position of the particles at each particle time sub-step different from the original method only updating the drag force at each CFD time step. The effect of fluid force on particles is described as true as possible, which improves the calculation accuracy. The accuracy of the algorithm is verified by labyrinth channel experiment. A computational example is given by applying the improved CFD–DEM method to analyze the sand carrying law in horizontal well with different particle size distributions and a wellbore sand migration model is established. The progressiveness of this model is that it considers sand particles with different particle size distribution, which is not involved in previous studies. This article provides an efficient calculation method for solving two-phase flow in engineering, enriching the theory of solid–liquid flow.</p>

An optimized CFD–DEM coupling calculation method and application for liquid–solid two-phase flow

期刊论文
发表日期：

2025年8月20日

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Shanshan Liu

摘要

When using the unresolved CFD–DEM (computational fluid dynamics and discrete element method) method to simulate two-phase flow problems of sand carrying in wellbore, the process of sand particle collision and deposition can be described from a mesoscopic perspective, but there is a contradiction between computational efficiency and computational accuracy. The traditional CFD–DEM method solves the two-phase flow by time incremental way. Setting the fluid solution time step as an integral multiple of the particle time sub-step can solve the problem of the accuracy of particle domain solution or efficiency of the fluid domain solution to a certain extent, but it will still lead to the low efficiency of fluid domain calculation or rough description of flow field details. The novel iterative convergence criterion and time advancement algorithm of fluid solid coupling are established by improving the solution strategy of unsolved CFD–DEM in terms of particle drag force by fluid. By introducing the velocity judgment threshold, the force acting on particles is updated for the calculation of the next DEM time sub-step when the relative velocity between fluid and particles is larger than the threshold and there is no need to update the force between the fluid and the particle at each particle time sub-step. If it is less than the given threshold, the force information of the particles at the previous position is used, which improves the calculation efficiency and ensures the calculation accuracy at the same time. After each DEM time step, the particle swarm domain information will be updated through extracting flow field information at the corresponding position of the particles at each particle time sub-step different from the original method only updating the drag force at each CFD time step. The effect of fluid force on particles is described as true as possible, which improves the calculation accuracy. The accuracy of the algorithm is verified by labyrinth channel experiment. A computational example is given by applying the improved CFD–DEM method to analyze the sand carrying law in horizontal well with different particle size distributions and a wellbore sand migration model is established. The progressiveness of this model is that it considers sand particles with different particle size distribution, which is not involved in previous studies. This article provides an efficient calculation method for solving two-phase flow in engineering, enriching the theory of solid–liquid flow.