Quantifying the efficiency of the acoustic radiation force from two-wave beating for structural resonance excitation of a thin spherical shell

Abstract

The structural echoes obtained from low-frequency (∼kHz) excitation of resonant underwater targets can serve as a basis for automated target recognition. Acoustic radiation force (ARF) can provide a means to excite those structural echoes with compact transducing mechanisms as it relies on high-frequency transducers to generate locally low-frequency excitation via the classical beating effect. However, a key question is quantifying the efficiency of ARF excitation mechanisms to excite those structural echoes when compared to using direct low-frequency pulses. Here, we develop a time-domain finite element framework that compares the ARF and direct low-frequency excitation methods to excite classical resonances scenarios such as thickness resonances of a thin plate or the so-called “mid-frequency enhancement echo” for elastic spherical shells. These canonical target objects provide a straightforward procedure to investigate the ARF excitation efficiency and establishes the numerical framework to investigate more complex targets with a wider range of environmental parameters.