Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing, 100044, China.
Department of Civil Engineering, University of Siegen, Siegen, 57068, Germany.
Sci Rep. 2017 Jun 29;7(1):4368. doi: 10.1038/s41598-017-04512-z.
A design strategy and its modeling for high-transmission acoustic self-focusing and directional cloaking in a two-dimensional (2D) and an axisymmetric three-dimensional (3D) gradient-index phononic crystal (GRIN-PC) are reported in this paper. A gradient perforated aluminum slab sandwiched by water is considered. A low-loss directional cloaking device is achieved by controlling the matching coefficient between the slab and the water. The anisotropy coefficient that affects the scattering properties is also introduced. Furthermore, the phase discontinuity for directional cloaking inside and outside the slab is overcome by introducing a non-gradient slab having a lower group velocity behind the GRIN slab as an acoustic delay device. In addition, an axisymmetric 3D directional cloaking structure is obtained by rotating the corresponding 2D structure around the slab axis.
本文报道了一种在二维（2D）和轴对称三维（3D）梯度折射率声子晶体（GRIN-PC）中实现高声学自聚焦和定向隐身的设计策略及其建模。本文考虑了由水夹在中间的梯度穿孔铝板。通过控制板和水之间的匹配系数，可以实现低损耗的定向隐身装置。此外，还引入了各向异性系数来影响散射特性。进一步地，通过在 GRIN 板后面引入具有较低群速度的非梯度板作为声延迟装置，可以克服板内和板外定向隐身的相位不连续性。此外，通过绕板轴旋转相应的 2D 结构，可以得到轴对称 3D 定向隐身结构。
