Experiments on nonlinear harmonic wave generation from colliding internal wave beams

Internal waves are abundant in both the ocean and atmosphere. Their propagation and breaking are essential to energy transfer and dissipation. However, nonlinear generation of harmonic waves due to interactions among internal waves of the same scale has not been adequately explored experimentally. When two nonresonant internal waves collide, harmonics are formed at the sum and difference of multiples of the colliding waves' frequencies, transferring energy from the initial wave beams to the harmonics. Here we experimentally explore interactions between nonresonant internal waves of the same scale and determine the relative kinetic energy transfer to their harmonics for eight unique configurations. We compare the harmonics generated here to those determined through the analysis of Tabaei et al. (2005) [1] and Jiang and Marcus (2009) [2]. It is found that approximately 7-16% of the original relative kinetic energy of the two interacting waves is transferred to the harmonics discussed here. For these configurations this value is more dependent on the relative direction the colliding waves approach each other than on their particular frequencies.