Triadic instabilities of internal wave standing modes

For a stratified fluid in a closed geometry, high amplitude internal waves can be generated by forcing global modes of the domain. These waves can then destabilize through triadic resonant instability (TRI), generating secondary waves. This experimental study, together with an interpretation based on a weakly nonlinear analysis, shows that the combination of box resonance conditions and nonlinear resonance conditions governs the nature of the secondary waves, causing in some cases a significant deviation from the internal waves dispersion relation and in general complex nonlinear interaction dynamics, with multiple pairs of secondary waves appearing dynamically.