论文标题
圆柱声外部斗篷的时间域调查
Time-domain investigation of a cylindrical acoustic external cloak
论文作者
论文摘要
基于非单调转换的空间折叠技术导致一类新的圆柱形各向同性声学斗篷，具有恒定的负密度和空间变化的负散装模量。我们考虑了一个外部斗篷，该斗篷由具有正定密度矩阵和正压缩性的核心组成，并且具有同时负密度和可压缩性的外壳。这样的核心壳共振系统在外壳之外创建了一个虚拟折叠区域。为了处理时间域中的这种负物理参数，使用了两步策略：（i）假设频率域中的有效参数共振（drude-type）； （ii）通过应用辅助场的形式主义返回时间域。我们从数字上表明，在设计的中心频率下，在有限的小刚性障碍物上散射入射的圆柱压力波在时间段落后，将其放置在外部斗篷的近距离附近时会大大降低。但是，在短时间内，外部斗篷的行为就像一个超隔板：斗篷本身比散射器集更散射。
Space folding techniques based on non-monotonic transforms lead to a new class of cylindrical isotropic acoustic cloaks with a constant negative density and a spatially varying negative bulk modulus. We consider an external cloak consisting of a core with a positive definite density matrix and a positive compressibility, and a shell with simultaneously negative density and compressibility. Such a core-shell resonant system creates a virtual folded region outside the shell. To handle such negative physical parameters in the time-domain, a two-step strategy is used: (i) assuming resonant (Drude-type) effective parameters in the frequency-domain; (ii) returning to the time-domain by applying the formalism of the auxiliary fields. We numerically show that, at the designed central frequency, scattering of a cylindrical pressure wave incident upon a finite set of small rigid obstacles is drastically reduced after a lapse of time, when they are placed in the close neighborhood of the external cloak. However, at short times, the external cloak behaves rather like a superscatterer: the cloak itself scatters more than the set of scatterers.
