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Inversion des perturbations de surface par traitement d'antenne en guide d'onde ultrasonore

Abstract : In shallow waters, the fluctuations of the water surface greatly affects the performances of underwater acoustic arrays. The goal of this thesis is to use tomography to detect, localise and estimate a travelling surface wave on the surface of an ultrasonic waveguide.The frame of this work is a small scale experiment. Two emitting and receiving arrays facing each other at each end of the waveguide create a acoustic pressure field of central frequency f=1 MHz which is projected on the basis of the eigenbeams using double beamforming performed simultaneously on the emission and on the reception. Each one of these eigenbeams is defined by four observables : the acoustic travel-time, the amplitude of the signal and the emitting and receiving angles. The Sensitivity Kernel (SK) approach allows to link the acoustic observables with the local displacement of the surface.The Bayesian inversion of the SK allows to accurately monitor and estimate the propagation and decay of a wave caused by a point excitation of the surface of the waveguide. Different energies of excitations are used, generating gravity-capillary waves of heights ranging from 0.01 mm to 1 mm. Optical measurements validate the estimation of the water displacement height.
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Submitted on : Thursday, February 27, 2020 - 4:02:40 PM
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  • HAL Id : tel-02493196, version 1

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Tobias van Baarsel. Inversion des perturbations de surface par traitement d'antenne en guide d'onde ultrasonore. Acoustique [physics.class-ph]. Université Grenoble Alpes, 2019. Français. ⟨NNT : 2019GREAU035⟩. ⟨tel-02493196⟩

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