On the energy transfer of tsunamis generated by subaerial granular landslides: A 2D numerical analysis

Tsunamis generated by landslides represent a significant hazard in coastal, fjord and lake environments. Their accurate modeling, using both physical and mathematical models, is crucial for activities such as risk assessment and mitigation strategies. Both approaches can provide valuable insights on the physics of landslide-tsunamis; however, due to the very complex nature of the problem, more efforts are needed to further understand the basic process of tsunami generation and propagation. In this sense, the study of the problem from an energetic perspective can provide valuable information, especially focusing on the energy transfer mechanisms between landslides and water waves. This paper presents a two-dimensional (2D) numerical study aimed at the energy mapping of tsunamis generated by subaerial granular landslides. To this end, several parametric simulations are carried out with OpenFOAM®, systematically varying some selected governing parameters (landslide falling height, water depth, and slope angle). For each simulation, several dimensionless energy quantities were computed and analyzed to investigate the energy transfer mechanisms between the landslide and the water waves. Further, the ability of some parameters to describe the efficiency of the energy transfer process for tsunami generation and propagation is investigated. At least for the cases considered in this study, it appears that the shape of the landslide vertical front at the impact and the extent of the submerged path are more important than the landslide velocity at the impact in terms of tsunamis generation efficiency. Finally, synthetic energy quantities have been examined from a broader perspective to derive overall insights into the energy transfer process between subaerial granular landslides and tsunamis, leading to the formulation of a first basic version of a nondimensional energy wavemaker curve.