A general numerical model for surface waves generated by granular material intruding into a water body

Surface water waves generated by large-scale landslides have been a major concern of many geoscientists and coastal engineers because they may result in disastrous consequences. This study presents an advanced two-phase model for dry granular material intruding into an otherwise still water body as well as their resulting waves. The water-air interface both within and outside the granular material is captured by the volume of fluid method. The inter-granular stresses are formulated based on a general collisional-frictional law developed for underwater granular flows and a modified k - epsilon model is adopted to describe the turbulence effect of the ambient fluid. Phase interaction is characterized by the drag force caused by the relative motion between the granular particles and the fluid. The effect of the ambient fluid on the restitution coefficient of granular particles is also considered. The newly proposed two-phase model is validated following a reasonable agreement of the numerical results with measured data from small-scale laboratory tests on surface waves caused by collapse of a subaerial granular column and by intrusion of a landslide into water. Generation and propagation of the waves, as well as the motion and deformation of the granular body, are all adequately represented by the numerical model. A relatively more general applicability of the proposed model to the study of waves generated by granular landslides can thus be expected.