Internal subharmonic resonance in faraday experiment

The classical Faraday experiment is a tractable problem in nonlinear physic s, and its rich spectrum of nonlinear phenomena has made it a prototype in studying nonlinear wave dynamics in general. Here we report the observation of a new type of subharmonic resonances which occurs at some smaller fract ional frequencies, such as nu/3, nu/4, and nu/6, where nu is the forcing fr equency. As a result of these resonances, the lower-order surface-wave mode s whose eigenfrequencies are dose to the fractional frequencies participate into the wave motions. Our theory involving quadratically nonlinear mode c ouplings shows that an already excited mode itself can act as a. parametric source on the lower-order primary modes, thus leading to the cascading sub harmonic resonances.