Berkeley Fluids Seminar

Wednesday, April 27, 2016

240, Bechtel Hall, 13:00-14:00

Louis-Alexandre Couston (Mechanical Engineering, UC Berkeley)

Resonant Interactions of Surface and Internal Waves with Seabed Topography

Abstract: Surface and internal waves propagating over a flat or mildly sloped seabed can travel long distances undisturbed. In the presence of small periodic corrugations on the seafloor, however, incident waves can be significantly affected by the variations of the seabed and experience strong resonant reflections. In this talk, we will investigate theoretically and with numerical simulations several arrangements of small seabed corrugations which lead to significant wave transformations, and which are different than the classical wave reflection. Specifically, we will show that water waves on the ocean’s surface traveling over seabed corrugations can become trapped and amplified, or deflected at a large angle (~90°) relative to the incident direction of propagation. Internal waves propagating over seabed topography can exhibit similar behaviors, but more surprising and intricate internal wave dynamics can also be obtained. Indeed, unlike surface waves, internal waves interacting with monochromatic seabed corrugations can simultaneously generate many new waves with different wavenumbers and directions of propagation—a phenomenon called chain resonance. The chain resonance will be shown to lead to significant energy transfer from long internal waves to short internal waves, which may have important consequences on the spatial variability of ocean mixing and energy dissipation. In conclusion, potential applications of the theory of resonant wave-seabed interactions for wave energy extraction and coastal protection will be discussed.

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Acknowledgments

Prof. Graham Fleming (Vice Chancellor for Research, UC Berkeley)

Prof. Eliot Quataert on behalf of The Theoretical Astrophysics Center and the Astronomy Department (UC Berkeley)

Prof. Philip S. Marcus on behalf of the Mechanical Engineering Department (UC Berkeley)

Prof. Michael Manga (Earth and Planetary Science, UC Berkeley)

Prof. Evan Variano (Civil and Environmental Engineering, UC Berkeley)