Stratified turbulence produced by internal wave breaking: two-dimensional numerical experiments

This study investigates the strongly nonlinear regime resulting from internal wave breaking in stratified fluids, employing two-dimensional numerical computations to elaborate on the prior research that showed wave breaking occurs regardless of amplitude. The research analyzes the instability mechanisms and finds that buoyancy and velocity variance spectra exhibit wavenumber scaling consistent with theoretical predictions, specifically as 0.2N2k~ -3 and 0.1N2k~ -3, where N represents the Brunt-Väisälä frequency and k the vertical wavenumber. The buoyancy variance spectrum aligns closely with laboratory experiments and resembles oceanic temperature spectra. Notably, the spectrum of buoyancy flux reveals a counter-gradient behavior at smaller scales, supporting findings from earlier numerical simulations. A physical interpretation for this phenomenon is proposed, and the dynamics of buoyancy flux are compared with kinetic energy and buoyancy variance spectra to assess energy transfer mechanisms. These comparisons are essential in addressing the prevailing theories related to the k -3 spectral range, also visible in the stratosphere. This research provides insights into the turbulent processes in stably stratified fluids and the significance of wave breaking in oceanographic contexts.