Ocean is density-stratified due to vertical gradients in salinity and temperature in deep water and can become stratified in shallow waters due to sediment resuspension. The stratified density structure supports the generation of waves in ocean interior (internal waves). My research has been focused on generation of internal waves over topography and energy transfer from surface waves to internal waves due to nonlinear interactions.

Internal Tides

Propagation of barotropic (or surface) tides over bathymetric features such as deep ocean ridges, seamounts, and continental shelf break causes a strong disturbance in background density field that releases potential energy in the form of internal wave beams. Internal tides are internal waves with tidal frequency. It is now well known that  internal tides are a major driver of mixing in ocean interior. Although internal tide generation is expected from linear theory and is dominantly hydrostatic, the accompanied nonlinear and nonhydrostatic processes result in significant  turbulent mixing and dissipation.  We study the energetics of the generation process and the physics of internal wave evolution using analytical models and high resolution numerical simulations. 

Related publications:

Tahvildari, N., O. B. Fringer, and T. Peacock (2014) " A parametric study of nonlinear internal tide generation over a submerged ridge", in preparation for Journal of Physical Oceanography

Nonlinear wave processes in two-layer density-stratified fluids

As intense density variation is confined to a thin layer (thermocline or pycnocline) above and below which density variation is small, a two-layer configuration is often an acceptable model to study the general dynamics of oceanic flows. In a two-layer system, two modes of motion, surface and interfacial, exist. Nonlinearity in the governing equations provides a way for these modes to exchange energy. We develop and apply analytical and numerical models to study the coupling between waves in this system.