Internal gravity wave dynamics in a rotating and stratified fluid

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CBET-0755114Swinney Internal gravity waves are ubiquitous in lakes, oceans and the atmosphere, due to the density stratification present in these environmental fluid bodies. Internal gravity waves affect acoustic transmission, sediment transport and off-shore platforms. These waves are also a major driving mechanism for the general circulation of the ocean. The goal of this research is to use laboratory experiments and numerical simulations is to better understand the fundamental fluid dynamics underlying the generation, interaction and breaking of internal gravity waves. The experiments will be conducted in a stratified and rotating fluid using Particle Image Velocimetry, a conductivity probe, and fluorescent dye visualization. Pseudo-spectral numerical experiments will complement the laboratory experiments. Specifically, the PIs will study harmonic wave generation by internal gravity wave-wave interactions, internal wave generation and mixing over a sloping boundary, and latitudinal dependence of the parametric subharmonic instability. Detailed spatiotemporal data will be obtained in regimes where appropriate theoretical models do not exist and field observations provide sparse data. Systematic variation of parameters in the experiments and simulations will help reveal the underlying physics. Experiments on nonresonant wave-wave interactions will improve the current picture of energy exchange between waves. Experiments on internal wave generation will quantify a new mechanism that can produce strong boundary flow and turbulent mixing in lakes and continental margins. Experiments on the parametric subharmonic instability will help to understand the global internal gravity wave dissipation in oceans. Understanding of the fundamental physics revealed by this research will enhance the ability to quantify the role of internal gravity waves in lake, oceanic and atmospheric dynamics. Besides the environmental applications, experiments on nonresonant wave-wave interactions may also have impact on the understanding of waves in strongly magnetized plasmas, where there exist waves (e.g., in tokamaks) with the same dispersion relation as internal gravity waves. Further, this type of wave plays an important role in the dynamics of White Dwarfs and Neutron Stars.