Non-Spherical Particle Modelling in Fluid Flow Using DEM-CFD Coupling

In numerical models, particles are usually simplified and assumed to be spheres. However, particles are typically irregular shaped in many real-life industrial applications, such as sedimentation, mineral processing, agricultural and more. Most of these applications involve modelling of gas-solid flow. Thus, the dynamics of non-spherical particles in fluid is of great interest. Early investigations have been focussing on drag over spheres in fluids. For non-spherical particles, the drag and lift forces will be a function of its orientation against the fluid. Torque on the particles induced by the hydrodynamics forces will need to be included as well.

DEM-CFD coupling model has been an emerging approach in particle-fluid interactions modelling. It has been successfully applied in many gas-solid flow applications, such as pneumatic conveying and fluidised beds. In DEM, a method to utilise spheres to approximate the shapes of non-spherical particles and to model their dynamics is well-established. This method is employed in the leading commercial DEM software, EDEM. However, in gas-solid flow, DEM-CFD calculations of hydrodynamic forces and toques on non-spherical particles are often based on spherical assumptions. There are drag and torque models devised for non-spherical particles tracking in fluid, but these models mainly work well in uniform flow.

In this paper, the hydrodynamic models for non-spherical particles in uniform flow have been implemented. We also propose a simple model that would extend the original model to take into account the velocity gradient around a non-spherical particle in non-uniform flow, e.g. jet acting on part of a cylinder. The model has been validated against an experiment, where a cylinder is dropped into a rectangular fall tube. The model is then applied to an industrial application setup to demonstrate the potential of this model in flow with uniform and non-uniform fields.