Hydro-mechanical analysis of calcareous sand with a new shape-dependent fluid-particle drag model integrated into CFD-DEM coupling program

Abstract

In this study, a new shape-dependent fluid-particle drag model for irregularly shaped particles is integrated into the fluid dynamic program CFD-DEM and used to analyse the behaviour of calcareous sand particles in liquids. The new drag model had been correlated by pervious settling experiments of calcareous sand particles in a static Newtonian Liquid. The new drag model defines the particle-fluid drag coefficient as a function of both the fluid regime and particle shape characteristics which can evaluate how the particle shape deviates from a regular sphere. This study is a follow-up work of the authors' previous experimental research, focusing on the numerical modelling of sand particle-fluid interaction. To validate the integration of the new drag model in program CFD-DEM, the code has been used to reproduce the calcareous sand particle settling and seepage experiments. The comparison with simulations using the existing drag models without considering particle shape effect demonstrates that, by means of the new drag model, a significant improvement in the capability of CFD-DEM program to predict the terminal falling velocity of irregularly shaped particles is obtained. With this implementation, CFD-DEM program is used to simulate seepage flows within calcareous sand sample in which particles are significantly different from regular spheres, as is usually the case of environmental and geological fluid-particle flows.