Numerical modeling of tsunamis generated by granular landslides in OpenFOAM®: A Coulomb viscoplastic rheology

Abstract

Landslide-generated tsunamis are a relevant hazard. Their low frequency/high consequences character and the complex phenomena related to their generation, propagation and interaction with the shore make the proper modeling of these phenomena a crucial activity to mitigate the related risk. In this article, a new numerical method for modeling tsunamis generated by granular landslides in OpenFOAM® is presented. The approach consists in modeling the granular material by using a Coulomb viscoplastic rheology (non-Newtonian rheology) implemented in the standard solver multiPhaseInterFoam. The proposed approach is simple as it only depends on few physics-based parameters, thus implying less uncertainties than dense fluid models and more flexibility and computational efficiency than Euler?Euler approaches. This numerical framework is applied to reproduce three literature benchmark landslide-tsunami cases: two-dimensional (2D) submerged as well as 2D and threedimensional (3D) subaerial. Comparing numerical and experimental results, a good agreement is found for granular material behavior, while an overall very good (excellent in some cases) agreement is found as far as fluid behavior and waves characteristics are concerned, testifying that the momentum transfer between granular and fluid phases is well reproduced by this simple rheological model. Qualitative descriptions of the numerical results, in terms of landslide behavior, wave generation characteristics, and velocity field during the generation/propagation process are provided. Moreover, quantitative comparisons between experimental and numerical results by comparing landslide evolution, free surface elevation time series, and runup time series are presented and discussed in the article.