Finite Element Modeling of Acoustic Wave Scattering and Focus Tuning in Poroelastic Acoustic Lenses

International Journal of Physics | Vol. 8, No. 8, August 2017 | pp. 57–64

DOI: 10.46882/2017/IJP/000088

Research Article

Title: Finite Element Modeling of Acoustic Wave Scattering and Focus Tuning in Poroelastic Acoustic Lenses

Names of Authors: P. J. O’Connor¹, G. S. Campbell²

Authors’ Affiliations: ¹Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland; ²Research School of Physics and Engineering, Australian National University, Canberra, Australia

Abstract: Controlling acoustic focal positions and intensities in underwater and marine structural environments is essential for non-destructive testing, ultrasound medical imaging, and sonar technologies. This study implements a finite element modeling approach to simulate acoustic wave scattering and focus tuning within gradient-index poroelastic acoustic lenses. The design leverages a coordinate-transformation method applied to Biot's dynamic poroelastic equations to determine the required anisotropic distribution of density and elastic moduli tensors across the lens. We performed numerical scattering simulations across an ultrasonic frequency band from 30.0 kHz to 120.0 kHz. The computational models show that a hyperbolic lens constructed with 32 concentric sub-wavelength layers successfully concentrates an incident acoustic wave to a localized spot. This configuration increases the total acoustic energy density at the focal point by 12.0 dB at a design frequency of 80.0 kHz. We analyzed the impact of fluid viscosity on lensing performance, finding that viscous dissipation in the porous channels dampens higher-order harmonic fields. This damping restricts forward transmission to a minor 5.5% energy loss. Experimental validation was carried out using 3D-printed perforated elastomeric matrices immersed in water. The measured pressure fields matched the simulated profiles within a ±5.0% margin.

Keywords: Acoustic metamaterials; finite element modeling; acoustic lenses; Biot's theory; focus tuning; porous media

Manuscript Timeline: Received: April 15, 2017; Revised: June 02, 2017; Accepted: June 22, 2017; Published: August 18, 2017

Citation: O’Connor, P. J., & Campbell, G. S. (2017). Finite Element Modeling of Acoustic Wave Scattering and Focus Tuning in Poroelastic Acoustic Lenses. International Journal of Physics, 8(8), 57–64.

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