Experimental validation of a broadband pentamode elliptical-shaped cloak for underwater acoustics

In this paper we report the numerical design and experimental validation of a pentamode cloak for scattering reduction elliptical targets in underwater acoustics. Despite being well-known theoretical concept, validations transformation-based acoustic cloaking non-axisymmetric have been hindered due to difficulties related complexity required material distribution. We overcome these by adopting linear quasi-symmetric map defined elliptic coordinates that allows with constant anisotropic elasticity scalar inhomogeneous density. then perform long-wavelength homogenization based optimization unit cells implement computed Numerical allow assess working range designed microstructure, which depends solely on ratio between wavelength size is thus expressed terms maximum normalized wavenumber κ L c , characteristic length considered cell. The influence performance bandgap common all microstructure also discussed, finding it actually detrimental reduction. Finally, specimen fabricated experimentally tested over 0 . 45 < 1 34