Design and Simulation of Acoustic Metamaterial Lune-burg Lenses for Predetermined Focal Points

The design and simulation of acoustic metamaterial lenses for focusing elastic waves at pre-determined focal points are presented in this article. Based on modified Luneburg refractive index profiles, three distinct lenses are designed, each to target specific focal points. A key contribution is the proposal of hexagonal unit cells containing blind holes with varying diam-eters. Finite element simulations are conducted to obtain dispersion curves, determining each unit cell's wave properties, including the refractive index. These unit cells provide a wide range of refractive indices from 1.0314 to 1.4959 at the design frequency of 50 kHz which is suitable for constructing the desired lenses. Unit cells are then arranged according the afore-mentioned discretized profiles to shape the required lenses. Numerical simulations validate effective elastic wave focusing at the intended focal points (F=R, 1.5R, 2R) with three lenses. The strongest wave concentration occurs at focal points closer to the lens, with the design for F=R achieving the highest level of focusing based on maximum velocity values. As the focal point shifts from R to 2R, the wave distribution becomes scattered along the focal axis, which is believed to be appropriate for acoustic/elastic jet applications. This study demonstrates the potential of these lenses in precisely controlling acoustic/elastic wave propagation, which has significant applications in enhancing resolution and accuracy for non-destructive testing, in-dustrial imaging, and optimizing energy harvesting.

Design and Simulation of Acoustic Metamaterial Lune-burg Lenses for Predetermined Focal Points Keywords:

Acoustic Metamaterials , Luneburg lens , Predetermined Focal Points , Elastic Waves.