UMR 5672

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Surface waves interacting with mean flows: from the ocean to the laboratory

Basile Gallet (SPEC, CEA Saclay)
When Jan 15, 2018
from 11:00 AM to 12:00 PM
Where Amphi Schrödinger
Attendees Basile Gallet
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I will present studies on the interaction between surface waves and mean flows, both in an oceanographic context and in controlled laboratory experiments. The oceanographic context is the propagation of the swell generated in stormy regions of the globe. Such long ocean surface waves propagate over thousands of kilometers before breaking on distant beaches. Using a directional receiver located a few kilometers from the shore, one can infer the sources of incoming swell events. The inferred sources most often coincide with storms reported on weather maps. However, there are some puzzling failures, where the inferred source is located on the Antarctic continent. Using ray-tracing through the surface currents inferred from satellite altimetry, I will show that such mirages result from the refraction of swell by oceanic mesoscale eddies. Motivated by this natural example, we designed a controlled laboratory experiment where surface waves impinge on a steady vortex. Wave refraction is associated to a wave-induced recoil force on the vortex: intense waves displace the vortex and distort it. I will introduce simple theoretical models to characterize this phenomenon and derive its governing scaling-laws. Such wave-induced vortex distortions have important consequences for the nonlinear regime of wave refraction: the refraction angle rapidly decreases with wave intensity.

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