3-D underwater acoustic wave focusing by periodic structure

By assembling the square lattice arrays of “+” shaped steel rods, an underwater acoustic composite lens consisting of a convex lens and a slab lens is proposed to achieve the convergence of underwater acoustic waves. In order to study the focusing ability, numerical simulations and experiments in a silencing pool are carried out among a range of frequencies between 15 kHz and 25 kHz. As a result, the 3-D underwater acoustic wave focusing is inspiringly achieved and observed. Particularly, the proposed underwater acoustic composite lens is vertically extended from a 2-D convex lens, but it is found to be able to focus waves in a three-dimensional manner. Comparisons of wave intensities and the focal distance between the numerical results and experimental results show fair agreements. These findings pave the way to the usage of superlens, hyperlens, and Luneburg lens for 3-D underwater acoustic wave focusing.