声学黑洞研究进展与应用

The problem of vibration and noise has always been one of the difficulties in the development of society. Therefore, the innovation of vibration and noise reduction methods has never stopped. In recent years, the introduction of acoustic black holes to manipulate flexural waves has become a hot topic in the field of vibration and noise. In this review, the acoustic black hole is defined as a kind of structure which can converge the flexural wave by changing the geometric parameters or material properties. In the absolute ideal case, the flexural wave velocity gradually decreases to zero in the acoustic black hole region. Acoustic black hole structures, as a new kind of flexural wave manipulation technique, can effectively reduce the propagation speed of flexural waves in the structure, thus reducing the reflection at the end of the boundary and forming a region with high energy density. Therefore, it has a broad application prospect in vibration reduction, noise reduction, fluctuation control and energy recovery. Different from the composite structure of vibration reduction and noise reduction in the past, the acoustic black hole has some certain advantages in practical application because of its simple structure, material and preparation process. Up to now, a great deal of theoretical modeling and experimental research has been carried out on the structural form of acoustic black holes, and some certain research results have been obtained. This review first introduces the origin, basic definition and principle of acoustic black holes, then introduces the theoretical calculation and experimental research methods, including frequency domain methods (semi-analytical method, Gauss expansion method, geometric acoustics method, transfer matrix method, finite element method, unit decomposition finite element method, spectral element method, and finite difference method) and wave-number domain method. Additionally, the laser ultrasonic scanning technology is emphasized in the experimental research. Next, the four main functions of acoustic black holes are classified and described, which are vibration reduction, noise reduction, fluctuation control and energy recovery, and the research status and existing problems of each application direction are summarized. The application of acoustic black holes in vibration reduction and noise reduction is becoming more and more comprehensive, and its applications in wave regulation and energy recovery are emerging in recent years. As a new research direction, the basic theory and practical application of acoustic black holes still need to be widely studied further. The breakthrough points include: (1) The acoustic vibration coupling mechanism of acoustic black holes and the matching with functional materials need to be further clarified; (2) the nonlinear wave behavior in acoustic black holes needs to be further improved; (3) according to different engineering scenarios, the bearing integrated design method of acoustic black hole composite structures is developed; (4) theoretical modeling and application development of imperfect acoustic black hole structures. The development of acoustic black holes is also a supplement and broadening to the related research of vibration and noise reduction. From the perspective of social development needs, the related research of acoustic black holes has potential applications in the independent research and development of functional structures and materials.