Theories and Applications of CFD–DEM Coupling Approach for Granular Flow: A Review

Bio-particulate matter includes grains, cereal crops, and biomass that are considered discrete materials with irregular size and shape. Although the flow of these particles can behave like a continuum fluid at times, their discontinuous behavior cannot be simulated with traditional continuum-based modeling. The Discrete Element Method (DEM), coupled with Computational Fluid Dynamics (CFD), is considered a promising numerical method that can model discrete particles by tracking the motion of each particle in fluid flow. DEM has been extensively used in the field of engineering, where its application is starting to achieve the popularity in agricultural processing. While CFD has been able to simulate the complex fluid flows with a quantitative and qualitative description of the temporal and spatial change of the flow field. This paper reviews the recent strategies and the existing applications of the CFD–DEM coupling approach in aerodynamic systems of bio-particles. It mainly represents four principal aspects: the definition of aerodynamic systems with its principals, modeling of particle motion including interaction forces of particle–particle and particle–fluid in the system, CFD–DEM coupling methodologies, and drag correlation models with theoretical developments, and the applications of aerodynamic systems related to the agricultural field. The existing published literature indicates that CFD–DEM is a promising approach to study the bio-particulate matter behavior immersed in fluid flow, and it could be benefiting from developing and optimizing the device's geometry and the operations. The main findings are discussed and summarized as a part of the review, where future developments and challenges are highlighted.