Material-Based Comparative Design and Simulation of Underwater Ultrasound Acoustic Metamaterial Luneburg Lenses

Acoustic metamaterial Luneburg lenses are an important group of gradient refractive index acoustic lenses designed for accurate wave focusing. In recent years, researchers have explored various ۲D and ۳D Luneburg lens structures with unique unit cell designs. However, a lack of comparative and material driven designs of acoustic metamaterial lenses is noticeable, particularly regarding how using different materials for established unit cells affects focusing behaviour of the acoustic metamaterial lenses. Therefore, this article presents four underwater acoustic metamaterial Luneburg lenses, designed and simulated for working frequency of ۴۰ kHz using four common ۳D-printing materials: PLA, ABS, PETG and Nylon. The lenses are formed by cubic polymer unit cells with air inclusions acting as acoustic scatterers. Finite element simulations in COMSOL are performed to calculate the dispersion curves and refractive indices of the unit cells with varying filling factors. The unit cells are then arranged next to each other according to the general case of the Luneburg lens profile where the incoming waves are focused at a point on the boundary of the lens. The performance of these lenses is then evaluated by numerical simulations. The results of this study showed that the lenses made of Nylon and PLA successfully achieved the intended high intensity focal point with Nylon lens producing the highest pressure peak of ۲.۷۵ times the incident pressure amplitude and PLA lens achieving the narrowest full width at half maximum (FWHM) of ۰.۵۷۲. However, the lenses made of ABS and PETG failed to focus the incoming waves onto the predetermined focal point. The findings of this study provide a comparative understanding for designing acoustic metamaterial lenses which have a wide range of applications from industrial to medical fields.

کلیدواژه ها:

Acoustic metamaterials ، Luneburg Lens ، Underwater Acoustics ، Ultrasound