Impact of dissipation on the energy spectrum of experimental turbulence of gravity surface waves

TL;DR

This study investigates how dissipation and surface contamination affect the energy spectrum in gravity surface wave turbulence, revealing deviations from theoretical predictions and the role of bound waves at higher frequencies.

Contribution

It provides experimental insights into the impact of dissipation and contamination on wave turbulence spectra, highlighting the limitations of Weak Turbulence Theory at higher frequencies.

Findings

Clean water shows a power law spectrum up to 14 Hz.

Spectral exponent increases with forcing strength in clean conditions.

Surface contamination reduces the spectral exponent and spectrum extent.

Abstract

We discuss the impact of dissipation on the development of the energy spectrum in wave turbulence of gravity surface waves with emphasis on the effect of surface contamination. We performed experiments in the Coriolis facility which is a 13-m diameter wave tank. We took care of cleaning surface contamination as well as possible considering that the surface of water exceeds 100~m$^2$. We observe that for the cleanest condition the frequency energy spectrum shows a power law decay extending up to the gravity capillary crossover (14 Hz) with a spectral exponent that is increasing with the forcing strength and decaying with surface contamination. Although slightly higher than reported previously in the literature, the exponent for the cleanest water remains significantly below the prediction from the Weak Turbulence Theory. By discussing length and time scales, we show that weak turbulence cannot be expected at frequencies above 3 Hz. We observe with a stereoscopic reconstruction technique that the increase with the forcing strength of energy spectrum beyond 3~Hz is mostly due to the formation and strenghtening of bound waves.