A critical review of the coupled CFD–DEM method for the simulation of two-phase liquid–solid systems

Two-phase liquid–solid systems, such as mixing units, fluidized beds , hydraulic conveyors, and separation systems, are commonly found in various industries. The coupled CFD–DEM method has become a widely accepted approach for analyzing these systems due to its accuracy and versatility. However, it is common in the literature to apply the assumptions used in simulating gas–solid systems to liquid–solid contexts. This critical distinction is often overlooked: the forces of interaction between the fluid and particles, as well as the dynamics between particles, differ significantly in liquid–solid systems compared to gas–solid systems. Neglecting these differences can result in inaccurate simulations. This study emphasizes the key differences between using CFD–DEM for simulating liquid–solid systems versus gas–solid systems. The study also examines the capabilities of the CFD–DEM method in simulating various liquid–solid unit operations. Lastly, it identifies gaps in current CFD–DEM models and suggests areas for model improvement.