Dispersion equation for water waves with vorticity and Stokes waves on flows with counter-currents

TL;DR

This paper derives dispersion equations for water waves with vorticity, analyzing bifurcation from shear flows with counter-currents, and provides conditions for the existence of Stokes waves on finite-depth flows.

Contribution

It introduces new dispersion equations for bifurcating Stokes waves with vorticity and counter-currents, expanding understanding of wave formation in such flows.

Findings

Dispersion equations for bifurcating Stokes waves are derived.

Conditions for roots of dispersion equations are established.

Illustrative examples with specific vorticity distributions are provided.

Abstract

The two-dimensional free-boundary problem of steady periodic waves with vorticity is considered for water of finite depth. We investigate how flows with small-amplitude Stokes waves on the free surface bifurcate from a horizontal parallel shear flow in which counter-currents may be present. Two bifurcation mechanisms are described: for waves with fixed Bernoulli's constant and fixed wavelength. In both cases the corresponding dispersion equations serve for defining wavelengths from which Stokes waves bifurcate. Sufficient conditions guaranteeing the existence of roots of these equations are obtained. Two particular vorticity distributions are considered in order to illustrate general results.