Wave turbulence and intermittency in directional sea states

TL;DR

This paper investigates how wave directionality influences turbulence and intermittency in ocean surface waves, revealing that broader directional spreading reduces coherent structures but does not eliminate intermittency.

Contribution

It provides experimental evidence on the impact of wave directionality on turbulence and intermittency in realistic sea states, a topic previously studied mainly theoretically.

Findings

Broader wave spreading decreases likelihood of coherent structures.

Intermittency persists even with increased directional spreading.

Wave turbulence characteristics are affected by wave directionality.

Abstract

The evolution of surface gravity waves is driven by nonlinear interactions that trigger an energy cascade similarly to the one observed in hydrodynamic turbulence. This process, known as wave turbulence, has been found to display anomalous scaling with deviation from classical turbulent predictions due to the emergence of coherent and intermittent structures on the water surface. In realistic oceanic sea states, waves are spread over a wide range of directions, with a consequent attenuation of the nonlinear properties. A laboratory experiment in a large wave facility is presented to discuss the effect of wave directionality on wave turbulence. Results show that the occurrence of coherent and intermitted structures become less likely with the broadening of the wave directional spreading. There is no evidence, however, that intermittency completely vanishes.