一种含横向圆柱形空腔的声学覆盖层的去耦机理分析

在水下结构表面敷设去耦覆盖层是降低其声辐射的有效途径. 为了深入分析一种含横向无限长空腔的覆盖层的去耦机理, 本文将其等效为均匀介质, 建立了敷设这种覆盖层的单向基体板在线激励下的声辐射模型, 验证了计算模型的有效性, 并利用计算模型对含横向空腔覆盖层的去耦机理进行了分析. 研究结果表明: 基体板-覆盖层接触面的能量流以纵波能量为主, 而横波能量很小, 因而计算覆盖层的去耦特性时可以忽略横波的作用; 和均匀覆盖层相比, 横向空腔型覆盖层在中高频段极大地增强了基体板的力阻抗, 从而更有效地抑制了基体板的振速; 此外, 和均匀覆盖层相比, 横向空腔型覆盖层和水的阻抗失配更大, 使其在中高频具有良好的振动传递损失特性. 因此, 总体而言, 含横向空腔的覆盖层相比均匀覆盖层具有更好的中高频去耦性能.

Analysis of decoupling mechanism of an acoustic coating layer with horizontal cylindrical cavities

Introducing the decoupling coating is an effective way to reduce sound radiation from underwater structures. In order to investigate the decoupling mechanism of a viscoelastic coating layer with horizontal cylindrical cavities, such a coating layer is approximated to a homogeneous layer with equivalent material properties, and a theoretical model is also developed to predict the sound radiation from a finite plate with such a decoupling coating layer. #br#The validity of the theoretical model is confirmed by comparison with the finite element method; and the decoupling mechanism of the coating layer is discussed. Numerical analysis shows that: (1) The energy flow across the interface between the plate and coating layer is mainly conveyed by longitudinal waves. (2) At a low frequency, the coating layer has nearly no decoupling effect. (3) In contrast with a homogeneous coating layer, the coating layer with horizontal cavities can greatly enhance the mechanical impedance in the mid- and high-frequency areas; hence the mean square velocity is effectively suppressed in the same area. (4) Compared with the homogeneous coating layer, the coating layer with horizontal cavities has a larger impedance mismatch with water, thus it exhibits great vibration transmission loss. Therefore, in general, the coating layer with horizontal cylindrical cavities has a better decoupling performance than the homogeneous coating layer in the mid- and high-frequency areas.