In the underwater sonar or similar devices where the high pressure field is required, the concentrating and black hole like structures have important applications in harvesting energy systems of elastic waves. In this work, a new kind of active elastic metamaterials with cavities and an acoustic concentrator are presented. By the feedback control gain of piezoelectric diaphragms, we can obtain both the controllable effective bulk modulus and density within a wide frequency range. Based on the coordinate transformation method and by the feedback control on the periodic arrangement of acoustic cavities, an acoustic concentrator with multilayered alternative homogeneous materials can be achieved. Numerical results show that the acoustic wave is perfectly limited within the core region of the concentrator, which can enhance the acoustic energy. These characteristics with the tunable effective bulk modulus and density within a very wide frequency range are expected to be helpful for the design of practical acoustic concentrators.

在需要高压场的水下声纳或类似装置中，聚光和类似黑洞的结构在收集弹性波能量系统方面具有重要应用。在这项工作中，提出了一种具有空腔和声集中器的新型主动弹性超材料。通过压电膜片的反馈控制增益，我们可以在很宽的频率范围内同时获得可控的有效体积模量和密度。基于坐标变换方法，通过对声腔周期性排列的反馈控制，可以实现具有多层替代均质材料的声集中器。数值结果表明，声波完全限制在集中器的核心区域内，可以增强声能。