Dry granular collapse into a liquid: Role of viscous dissipation on granular flow regimes and associated waves

During the generation of free-surface waves in landslide-tsunami modeling, the importance of grain-fluid interaction is still not well identified. To clarify this, the present study examines experimentally the role of viscous dissipation on the dynamics of dry granular masses collapsing into a liquid pool, by varying both the grain size and liquid viscosity. The experiments reveal a richness in granular collapse regimes, from dilute- and dense-inertial to dense-viscous regimes, that significantly influence the entire wave train, while having limited impact on the leading and largest wave.