Journal of Fluid Mechanics


Internal wave beam propagation in non-uniform stratifications


a1 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA


In addition to being observable in laboratory experiments, internal wave beams are reported in geophysical settings, which are characterized by non-uniform density stratifications. Here, we perform a combined theoretical and experimental study of the propagation of internal wave beams in non-uniform density stratifications. Transmission and reflection coefficients, which can differ greatly for different physical quantities, are determined for sharp density-gradient interfaces and finite-width transition regions, accounting for viscous dissipation. Thereafter, we consider even more complex stratifications to model geophysical scenarios. We show that wave beam ducting can occur under conditions that do not necessitate evanescent layers, obtaining close agreement between theory and quantitative laboratory experiments. The results are also used to explain recent field observations of a vanishing wave beam at the Keana Ridge, Hawaii.

(Received November 06 2008)

(Revised July 11 2009)

(Accepted July 16 2009)

(Online publication October 30 2009)