Potential dominance of oscillating crescent waves in finite width tanks

Abstract

Recently, it has been proposed that the emergence of previously observed oscillating crescent water wave patterns, created by class II (three- dimensional) instabilities which are in principle not dominant, could in fact be explained as an artifact of a finite width tank, combined with a suppression of the class I (Benjamin-Feir) instability. Within this context, we investigate quantitatively the dominance of class II deep water wave instabilities for particular transversal wavenumbers, and it is shown that the regions where non-phase-locked (oscillating) crescent wave patterns are locally dominant is surprisingly large, particularly for low to moderate wave steepness. This is an important realization for both experimentalists and numerical modelers currently studying these phenomena. © 2005 American Institute of Physics.