Asymptotic behaviour of a linearized water waves system in a rectangle

TL;DR

This paper analyzes the asymptotic behavior of small-amplitude water waves in a shallow rectangular domain, showing convergence to a 1D wave equation with boundary control using advanced mathematical techniques.

Contribution

It introduces a novel approach using a change of variables and scattering semigroup to analyze the shallow water wave system's asymptotics.

Findings

Solution converges to 1D wave equation with Neumann control

Uses Trotter-Kato approximation theorem for analysis

Provides detailed Fourier series analysis of boundary operators

Abstract

We consider the asymptotic behaviour of small-amplitude gravity water waves in a rectangular domain where the water depth is much smaller than the horizontal scale. The control acts on one lateral boundary, by imposing the horizontal acceleration of the water along that boundary, as a scalar input function u. The state z of the system consists of two functions: the water level $\zeta$ along the top boundary, and its time derivative $\partial$$\zeta$ $\partial$t. We prove that the solution of the water waves system converges to the solution of the one dimensional wave equation with Neumann boundary control, when taking the shallowness limit. Our approach is based on a special change of variables and a scattering semigroup, which provide the possiblity to apply the Trotter-Kato approximation theorem. Moreover, we use a detailed analysis of Fourier series for the dimensionless version of the partial Dirichlet to Neumann and Neumann to Neumann operators introduced in [1].