Non-Hydrostatic Model for Simulating Moving Bottom-Generated Waves: A Shallow Water Extension with Quadratic Vertical Pressure Profile

TL;DR

This paper develops a non-hydrostatic, depth-averaged model extending shallow water equations to simulate waves generated by moving bottoms, such as tsunamis and landslides, with improved accuracy and solvability.

Contribution

It introduces an alternative elliptic system to accurately model non-hydrostatic effects without ambiguity, enhancing tsunami and landslide wave simulations.

Findings

Efficiently models undersea earthquake-generated tsunamis.

Accurately simulates landslide-generated waves.

Outperforms models with linear and simplified quadratic pressure profiles.

Abstract

We formulate a depth-averaged non-hydrostatic model to solve wave equations with generation by a moving bottom. This model is built upon the shallow water equations, which are widely used in tsunami wave modelling. An extension leads to two additional unknowns to be solved: vertical momentum and non-hydrostatic pressure. We show that a linear vertical velocity assumption turns out to give us a quadratic pressure relation, which is equivalent to Boussinesq-type equations. However, this extension involves a time derivative of an unknown parameter, rendering the solution by a projection method ambiguous. In this study, we derive an alternative form of the elliptic system of equations to avoid such ambiguity. The new set of equations satisfies the desired solubility property, while also consistently representing the non-flat moving topography wave generation. Validations are performed using several test cases based on previous experiments and a high-fidelity simulation. First, we show the efficiency of our model in solving a vertical movement, which represents an undersea earthquake-generated tsunami. Following that, we demonstrate the accuracy of the model for landslide-generated waves. Finally, we compare the performance of our novel set of equations with the linear and simplified quadratic pressure profiles.