Sound propagation in a model ocean with internal waves: experiments and simulations

We conduct laboratory experiments and numerical simulations in a laboratory tank where sound waves and internal gravity waves are simultaneously generated and detected. The tank contains a density-stratified fluid with internal gravity waves produced by a wave generator. Acoustic sources and receivers are arranged such that the acoustic track crosses the internal wave beam. The internal wave energy density, energy flux, and total power are determined from particle imaging velocimetry measurements. The internal wave field is also computed in direct numerical simulations of the Navier-Stokes equations, using a parallelized finite-volume based solver code. The fluctuations in sound speed and intensity are determined as a function of the acoustic track location and the internal wave amplitude, frequency, phase, and modulation frequency. This research is designed to achieve a better understanding of sound propagation and scattering by internal waves in the oceans. [This research was supported by ONR MURI Grant N000141110701 (WHOI). L.Z. acknowledges the support of the 2013-14 ASA F. V. Hunt Postdoctoral Research Fellowship.]