Experimental investigation of tsunami waves generated by granular collapse into water

TL;DR

This study experimentally investigates how granular collapses into water generate tsunami-like waves, revealing that the wave amplitude scales with the Froude number and is primarily influenced by the volume of grains entering the water.

Contribution

It provides new insights into the wave generation mechanism by granular collapses, emphasizing the role of the granular front's velocity and volume over grain density.

Findings

Wave amplitude scales linearly with Froude number.

Granular collapse acts like a moving piston displacing water.

Grain density has negligible effect on wave amplitude.

Abstract

The generation of a tsunami wave by an aerial landslide is investigated through model laboratory experiments. We examine the collapse of an initially dry column of grains into a shallow water layer and the subsequent generation of waves. The experiments show that the collective entry of the granular material into water governs the wave generation process. We observe that the amplitude of the wave relative to the water height scales linearly with the Froude number based on the horizontal velocity of the moving granular front relative to the wave velocity. For all the different parameters considered here, the aspect ratio and the volume of the column, the diameter and density of the grains, and the height of the water, the granular collapse acts like a moving piston displacing the water. We also highlight that the density of the falling grains has a negligible influence on the wave amplitude, which suggests that the volume of grains entering the water is the relevant parameter in the wave generation.