Two-dimensional pentamode materials with a square lattice for underwater cloaking

An innovative numerical study on underwater acoustic cloaking is presented, employing two-dimensional pentamode materials arranged in a square lattice configuration. The pentamode structure, composed of aluminum and submerged in water within an air background, achieves effective broadband cloaking with a lattice constant of 10 mm. The total scattering cross section is reduced to approximately 0.25 over the frequency range of 1 – 18 kHz. In addition, far field pressure distributions are analyzed, showing a reduction in scattered pressure amplitude from 0.1 Pa for the aluminum block to 0.05 Pa for the acoustic cloak, confirming significant scattering suppression and minimal disturbance to the surrounding acoustic field. The robustness of the cloak under realistic environmental factors, including hydrostatic pressure and water temperature variations, has also been investigated, demonstrating the design’s practical applicability. While prior studies have predominantly utilized hexagonal or circular lattice geometries, this work explores the relatively less-studied square lattice arrangement, indicating its promising potential for underwater acoustic cloaking applications. These results underscore the versatility of square-lattice pentamode microstructures for practical and reliable underwater stealth technologies.