Large mode-2 internal solitary waves in three-layer flows

TL;DR

This paper explores the existence and characteristics of mode-2 internal solitary waves in three-layer flows, revealing embedded solitary waves with zero oscillatory tails and their relation to conjugate states, through numerical analysis.

Contribution

It demonstrates the existence of mode-2 embedded solitary waves with specific parameter conditions and compares solutions of nonlinear and approximate models.

Findings

Embedded solitary waves with zero tail oscillations identified.

Branches of solitary waves extend beyond linear wave speeds.

Large amplitude embedded waves linked to conjugate states.

Abstract

In this paper, we investigate mode-2 solitary waves in a three-layer stratified flow model. Localised travelling wave solutions to both the fully nonlinear problem (Euler equations), and the three-layer Miyata-Choi-Camassa equations are found numerically and compared. Mode-2 solitary waves with speeds slower than the linear mode-1 long-wave speed are typically generalised solitary waves with infinite tails consisting of a resonant mode-one periodic wave train. Herein we evidence the existence of mode-2 embedded solitary waves, that is, we show that for specific values of the parameters, the amplitude of the oscillations in the tail are zero. For sufficiently thick middle layers, we also find branches of mode-2 solitary waves with speeds that extend beyond the mode-1 linear waves and are no longer embedded. In addition, we show how large amplitude embedded solitary waves are intimately linked to the conjugate states of the problem.