Acoustic ground cloaks revisited

Abstract

The unique material properties now obtainable with acoustic metamaterials have led to unprecedented control of acoustic wave propagation, resulting in many applications including acoustic cloaking. The two fundamental approaches in the development of a ground cloak are quasiconformal mapping [Li et al. Phys. Rev. Lett. 101, 203901 (2008)] and coordinate transformations [Popa et al. Phys. Rev. B. 83, 224304 (2011)]. The differences in the required material properties prescribed by these two approaches lie in the amount of anisotropy and inhomogeneity, as well as the size of the cloak relative to object. The coordinate transformation approach has been used to produce a realizable anisotropic homogeneous ground cloak in the acoustic domain. This presentation will highlight the findings of work that examined how advances in metamaterial development could lead to the realization of required material properties for ground cloaks, and explore alternative transformations to expand the applications for acoustic ground cloaks.

Wave propagation with long-range forces and mistuning effects

“…The growing interest upon these new materials stands in the chance to control vibrations and wave motion through the appropriate tailoring of the physical properties, without the need of external forces driven by an active control. Accordingly, a wide class of new applications arise both in the aerospace and mechanical engineering fields, ranging from cloaking, 5 energy absorption, 6 coupling of distant structures, 7,8 wave control, 9,10 but also swarm dynamics. 11,12 In all these cases, the new features produce effects in terms of changes in wave stability, the emergence of negative group velocity, 13 superfast group and phase propagation 14,15 and band gaps.…”