Tong Yunzhe, Wang Bin, Fan Jun, Liu Benqi, Pan Xiefan
Shanghai Marine Electronic Equipment Research Institute, Shanghai 201108, People's Republic of China.
Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University Shanghai 200240, People's Republic of China.
J Acoust Soc Am. 2020 Aug;148(2):984. doi: 10.1121/10.0001708.
The acoustic scattering from an infinitely long cylindrical shell with periodic lengthwise ribs is studied. The shell motion is described by the Donnell equations, and the lengthwise rib is modeled as an elastic beam whose motion is decomposed into longitudinal and flexural vibrations. A circumferential mode expansion is used to obtain numerical results for the scattering sound field. The backscattering characteristics in the far-field can be explained by the resonance and interference phenomena. It is shown that subsonic flexural waves can be generated and radiated by the ribs. Due to the periodical distribution of the ribs, there exist multi-order flexural Bloch waves in the circumferential direction. The multi-order flexural Bloch waves can form standing circumferential waves, which lead to a complex acoustic resonance. The attachments of the ribs to the shell can reflect an acoustic wave directly and the reflected wave will interfere with the specular reflection, which is dominant in the frequency-angle spectra with an increasing number of ribs. Furthermore, the flexural wave and flexural Bloch waves can radiate through the attachments and interfere with the specular reflection. However, the interference fringes in the frequency-angle spectra caused by the flexural wave and flexural Bloch waves are coincident at broadside.
研究了具有周期性纵向肋条的无限长圆柱壳的声散射。壳体运动由Donnell方程描述，纵向肋条被建模为弹性梁，其运动被分解为纵向振动和弯曲振动。采用周向模态展开来获得散射声场的数值结果。远场中的后向散射特性可以通过共振和干涉现象来解释。结果表明，肋条可以产生并辐射亚声速弯曲波。由于肋条的周期性分布，在周向存在多阶弯曲布洛赫波。多阶弯曲布洛赫波可以形成周向驻波，从而导致复杂的声共振。肋条与壳体的连接处可以直接反射声波，反射波将与镜面反射相互干涉，随着肋条数量的增加，镜面反射在频率-角度谱中占主导地位。此外，弯曲波和弯曲布洛赫波可以通过连接处辐射并与镜面反射相互干涉。然而，弯曲波和弯曲布洛赫波在频率-角度谱中引起的干涉条纹在宽边处是重合的。
