Downscale energy fluxes in scale-invariant oceanic internal wave turbulence

Abstract

Abstract

Experimental observations of internal wave turbulence transition in a stratified fluid

“…Internal gravity wave interactions in the weakly nonlinear regime occur among three waves, and such interactions provide a mechanism explaining the energy transfer among scales [9]. Wave turbulence theory was also applied to internal gravity waves [4,[10][11][12], and recently exhibited a candidate solution of the KZ spectrum citedematteis2021origins with a scaling law ω −1.69 , close to the empirical GM decaying slope. Other theories have been proposed to explain the dynamics leading to the observation of the GM spectrum, among which there are eikonal theories, where diffusion plays an important role [13], strongly nonlinear wave interactions, and wave diffusion by geostrophic turbulence [14] (see [15] for a comprehensive review).…”

“…We detrended the velocities by subtracting their temporal average before computing the bicoherence. Furthermore, we calculated a reference level of bicoherence by adding a random phase at each spatial coordinate at the numerator in (12). Values smaller than ten times the reference are considered non-physical and therefore discarded.…”

“…Since we do not consider rotation in the experiments presented here, we aim to force the waves at a frequency significantly lower than N . Furthermore, decreasing the forcing has the advantage of enlarging the frequency range between F and N , to observe a possible energy cascade to high frequencies [12].…”

Scale Separated Approaches to the Interaction of Oceanic Internal Waves, part I: Theory

“…A possible resolution can be found in recent characterizations of the internal wave kinetic equation Dematteis and Lvov (2021); Dematteis et al (2022) that appear to coincide in magnitude and scaling with the description of transports encapsulated within the Finescale Parameterization. That work is executed in a non-rotating context for which = 0 and contains both 'local' and 'extreme scale separated' interactions.…”

“…This leads to a description in terms of a Fokker-Planck, or generalized diffusion equation McComas and Bretherton (1977). An unfolding of these balances and the role of local vs extreme scale separated contributions is contained in Dematteis and Lvov (2021); Dematteis et al (2022).…”