Paper of Tom Bridges on frequency downshifting of water waves published in JFM

The paper “Modulation leading to frequency downshifting of water waves in the vicinity of the Benjamin–Feir transition“, co-authored by Dan Ratliff (Northumbria), Olga Trichtchenko (University of Western Ontario), and Tom Bridges, has been published in the Journal of Fluid Mechanics. It is published open access (link here). For Stokes water waves in finite depth near the Benjamin–Feir stability transition, there are two families of periodic waves, one modulationally unstable and the other stable. In this paper the authors show that these two families can be joined by a heteroclinic connection, which manifests in the fluid as a travelling front. By shifting the analysis to the setting of Whitham modulation theory, this front is in wavenumber and frequency space. An implication of the jump is that a permanent frequency downshift of the Stokes wave can occur. The picture below shows Figure 5 from the paper.