Collapse of partially and fully submerged granular column generating impulse waves: An empirical law of maximum wave amplitude based on coupled multiphase fluid–particle modeling results

Abstract

In this study, impulse waves generated by partially and fully submerged granular collapse are investigated using a modeling method coupling the volume of fluid and discrete element method. Of particular focus is the effects of geometrical and material parameters of granular samples on wave generation mechanisms, thereby determining the controlling factors of maximum wave amplitude, which were unclear or inconsistently reported in previous experimental studies. It is found that the relative submerged depth (i.e., the ratio of initial granular sample height to water depth) is the main geometrical parameter governing the maximum wave amplitude generated by partially and fully submerged granular collapse. The inter-particle friction of granular materials also influences the maximum wave amplitude via altering the material mobility and momentum transferred from particles to water during the collapse process. The density of the granular material, on the other hand, has a negligible effect on impulse wave generation. Based on numerical characterization, an empirical model of the maximum wave amplitude is proposed and validated against experimental data. Its practical application to estimate the maximum wave amplitude generated by partially submerged landslide events is also demonstrated, suggesting its potential for the hazard assessment of landslide-generated tsunamis.