Dynamic imaging of a capillary-gravity wave in shallow water using amplitude variations of eigenbeams

• Main Authors: Arrigoni, M. (Author), Bonnel, J. (Author), Kerampran, S. (Author), Mars, J.I (Author), Nicolas, B. (Author), Roux, P. (Author), Van Baarsel, T. (Author)
• Format: Article
• Language: English
• Published: Acoustical Society of America 2019
• Subjects: Acoustic wave propagation; Acoustics; Air; Amplitude perturbation; Beamforming algorithms; Capillary-gravity waves; Explosives; Gravity capillary waves; Gravity waves; Laser induced breakdown; Phase interfaces; Sensitivity analysis; Shallow water waveguide; Simultaneous measurement; Surface waves; Transfer matrix method; Ultrasonic experiments; Ultrasonic imaging; Waveguides
• Online Access: View Fulltext in Publisher

 Dynamic acoustic imaging of a surface wave propagating at an air-water interface is a complex task that is investigated here at the laboratory scale through an ultrasonic experiment in a shallow water waveguide. Using a double beamforming algorithm between two source-receiver arrays, the authors isolate and identify each multi-reverberated eigenbeam that interacts with the air-water and bottom interfaces. The waveguide transfer matrix is recorded 100 times per second while a low-amplitude gravity wave is generated by laser-induced breakdown at the middle of the waveguide, just above the water surface. The controlled, and therefore repeatable, breakdown results in a blast wave that interacts with the air-water interface, which creates ripples at the surface that propagate in both directions. The amplitude perturbations of each ultrasonic eigenbeam are measured during the propagation of the gravity-capillary wave. Inversion of the surface deformation is performed from the amplitude variations of the eigenbeams using a diffraction-based sensitivity kernel approach. The accurate ultrasonic imaging of the displacement of the air-water interface is compared to simultaneous measurements with an optical camera, which provides independent validation. © 2019 Acoustical Society of America.