Large-Scale Discrete Element Modeling for a Gas–Solid–Liquid Flow System

Abstract

Gas−solid−liquid three-phase flow systems are ubiquitous in chemical and energy engineering. To simulate the multiphase systems, the authors' group has developed a numerical method that couples the discrete element method (DEM) and the volume of fluid (VOF) method, where the local volume average technique is employed. When the unresolved DEM-VOF method is applied to industrial systems, there are two critical problems: one is the inflexibility to select the grid size for the gas−liquid−flow simulations, and the other is the heavy computational cost due to a large number of particles. To solve these problems, a novel numerical method is proposed by introducing the refined grid model and coarse-grained model into the unresolved DEM-VOF method. Two types of verification tests are performed to illustrate the adequacy of the new method. First, a water entry problem of solid particles is simulated to verify the combination of the refined grid model and the unresolved DEM-VOF method. Second, a gas−solid−liquid fluidized bed system is computed to verify the combination of the refined grid model, the coarse-grained DEM method, and the unresolved DEM-VOF method. Through the verification tests, it is demonstrated that the new method can flexibly give the grid size for the VOF regardless of the solid particle size. Besides, the new approach makes it possible to reduce the calculation time of the DEM to 4.6% of the original time. The new approach will drastically improve the numerical modeling for gas−solid−liquid flows from the viewpoint of efficiency, accuracy, and flexibility.

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