Experimental time reversal of water waves
Résumé
The phenomenon of the time reversal refocusing of gravity-capillary waves in water tank cavity has been studied experimentally. The injection of a short pulse imposed by the wave generator leads (after several reflections from the boundaries of the tank/obstacles) to the appearance of the complex pattern. By re-injection of the time-reversed signals in the corresponding measurement positions, the temporal and spatial refocalisation can be observed in the initial source point. Owing to the reverberating effect of the cavity, only few channels are sufficient to reconstruct the surface wave at the point source, even if the absorption is not negligible. Space-time resolved measurements of the waves during the refocusing allow to quantitatively demonstrate that the quality of the refocusing increases linearly with the number of re-emitting channels. Numerical simulations corresponding to water waves at larger scales, with negligible damping, indicate the possibility of very high quality refocusing. The wave elevation was measured with good accuracy in time and in space using an optical method (Fourier Transform Profilometry) based on the analysis of the deformation of projected fringes, recently adapted by our group for water waves characterization.
Domaines
Acoustique [physics.class-ph]
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