Experimental generation of axisymmetric internal wave super-harmonics

We present experimental evidence of the generation of super-harmonic internal wave fields through self-interaction in axisymmetric geometry. For Cartesian plane waves, the self interacting term in linearly stratified fluid is equal to zero. Switching geometry to a cylindrical domain and axisymmetric wave fields leads to additional nonlinear effects and allows for the generation of waves at twice the forcing frequency, whose spatial structure is selected by the internal wave dispersion relation and the geometry of the experimental domain.