Near-inertial parametric subharmonic instability of internal wave beams
Name
PhysRevFluids.2.074801.pdf
Size
515.09 KB
Format
Adobe PDF
Checksum (MD5)
f642bd56164bec2634bf38c27bd6458e
Author(s)
Karimi, Hussain H.
Akylas, Triantaphyllos R
Date Issued
July 2017
Journal
Physical Review Fluids
Publisher
American Physical Society (APS)
Citation
Karimi, Hussain H., and T. R. Akylas. “Near-Inertial Parametric Subharmonic Instability of Internal Wave Beams.” Physical Review Fluids, vol. 2, no. 7, July 2017. © 2017 American Physical Society
Version
Final published version
Abstract
Parametric subharmonic instability (PSI) of internal wave beams in a uniformly stratified fluid is discussed, for the case where the beam frequency is nearly twice the inertial frequency due to background rotation. Compared with generic PSI, beams of finite width are expected on physical grounds to be more vulnerable to subharmonic perturbations of near-inertial frequency, as these disturbances have small group velocity and stay in contact with the underlying beam longer, thus extracting more energy. A weakly nonlinear theory for such near-inertial PSI is developed in the "distinguished limit" where the effects of triad nonlinear interactions, dispersion, and viscous dissipation are equally important. This model is used to examine the linear stability of a uniform beam to infinitesimal perturbations under a "pump-wave" approximation, as well as the nonlinear development of PSI that takes into account the effect of the growing perturbations on the beam evolution. Near-inertial PSI is possible for beams of general locally confined profile, in sharp contrast to generic PSI which can arise only for quasimonochromatic beams whose profile comprises a sinusoidal carrier modulated by a locally confined envelope. The theoretical predictions are consistent with earlier numerical simulations of semidiurnal internal tide beams generated over the continental shelf break at latitudes above and below the critical value 28.8âN, at which the subharmonic semidiurnal frequency matches the local inertial frequency.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Mechanical Engineering
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1103/PHYSREVFLUIDS.2.074801
