Confinement effects on gravity-capillary wave turbulence

TL;DR

This study examines how physical confinement in a water wave tank influences gravity-capillary wave turbulence, revealing a coexistence of weak turbulence and discrete modes due to finite size effects.

Contribution

It provides experimental insights into the effects of finite system size on wave turbulence near the gravity-capillarity crossover, highlighting the coexistence of different turbulence regimes.

Findings

Coexistence of weak wave turbulence and discrete modes observed

Finite size confinement alters wave turbulence properties

Surface deformations reconstructed using space-time profilometry

Abstract

The statistical properties of a large number of weakly nonlinear waves can be described in the framework of the Weak Turbulence Theory. The theory is based on the hypothesis of an asymptotically large system. In experiments, the systems have a finite size and the predictions of the theory may not apply because of the presence of discrete modes rather than a continuum of free waves. Our study focusses on the case of waves at the surface of water at scales close to the gravity-capillarity crossover (of order 1~cm). Wave turbulence has peculiar properties in this regime because 1D resonant interactions can occur as shown by Aubourg \& Mordant. Here we investigate the influence of the confinement on the properties of wave turbulence by reducing gradually the size of our wave tank along one of its axis, the size in the other direction being unchanged. We use space-time resolved profilometry to reconstruct the deformed surface of water. We observe an original regime of coexistence of weak wave turbulence along the length of the vessel and discrete turbulence in the confined direction.