Energy spectra of internal waves in stratified fluid: Direct numerical simulations

To investigate formation mechanism of energy spectra, direct numerical simulations of oceanic internal waves based on a dynamic equation are performed. Our simulations demonstrate that the resulting energy spectra in inertial regions are not universal. Instead, energy accumulates in the horizontally longest waves. We provide evidence that formation of energy spectra in inertial regions is dominated by scale-separated interactions with this accumulation at the longest waves. These nonlocal interactions in the wavenumber space make it questionable that a universal spectrum might be observed in direct numerical simulations. Implications of these findings to the real oceans and universal oceanographic spectrum are discussed.