Triadic resonant instability in confined and unconfined axisymmetric geometries

We present an investigation of the resonance conditions governing triad interactions cylindrical internal waves, i.e. Kelvin modes, described by Bessel functions. Our analytical study, supported experimental measurements, is performed both in confined and unconfined axisymmetric domains. are interested two conceptual questions: can we find for a modes? What impact boundary on such resonances? In cases, show that sub-harmonics be spontaneously generated from primary wave field if they satisfy at least condition their frequencies form $\omega _0 = \pm \omega _1 _2$ . demonstrate resulting also spatially resonant, but radial direction may not exact geometries due to prevalence – key difference compared with Cartesian plane waves.