Antonin Coutant (Univ Le Mans) - waves in fast mean flows
In most natural contexts, mechanical waves interact with mean flows, which can drag them or stretch and squeeze their wave fronts (Doppler shift). When the velocity of the current becomes of the order of the wave propagation speed (in which case we will talk about a "fast" flow), a new class of physical phenomena emerges. I will discuss such phenomena in two independent contexts. The first is the propagation of acoustic waves in waveguides. A surface treatment is built on the waveguide, which slows down the propagation of acoustic waves, and allows us to reach supersonic regimes with slow flows. I will discuss several exotic
consequences of these flows, such as wave trapping or amplification. The second context is the study of surface gravity waves scattering on vortex flows. If the incident wave is shaped in the appropriate manner, it can extract energy from the flow during the scattering. I will explain this effect theoretically and present an experimental observation.
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- 2021-02-04 11:30