Semi-resolved CFD-DEM coupling model for submerged granular collapse

Submerged granular collapse involves strong interaction between fluid and particles, while the widely applied unresolved computational fluid dynamics-discrete element method (CFD-DEM) coupling model cannot accu-rately simulate the interaction when the particle-grid size ratio is >1/3. Herein, a semi-resolved CFD-DEM coupling model is employed to eliminate the size ratio limitation. This model approximates the ambient fluid variables required by the hydraulic force calculation within an expanded dependent domain, and allocates the particle volume and reacting drag force to fluid within an expanded influential domain. The performance of the semi-resolved model in simulating a submerged granular collapse is studied by comparing the numerical results with the experimental data in detail. Results show that the simulated deposit morphologies, including the sur-face, residual height, and runout distance of the granular columns, well agree with the measured data. Moreover, since the limitation on the size ratio is eliminated, the numerical simulations well reproduce the details of the collapse-induced fluid flows observed in experiments, especially the evolution of the shear vortex above the interface between fluid and particles.