内部体积源作用下的圆柱壳内外声场特性

圆柱壳内各型体积源辐射噪声特性研究是声场建模和声场预报的前提.为了研究具有指向性的大尺度体积源特性对水下航行器结构内外声场的影响,本文结合薄壳理论、等效源和柱腔Green函数构造了体积源激励下的壳体振动耦合方程,研究了体积源表面声散射作用和指向性强弱对圆柱壳内外声场的影响.数值计算结果表明,体积源构造的准确性与其等效源位置有关,等效源配置在体积源几何中心与其结构表面之间0.4—0.6时,可以提高声场计算结果的准确性;大尺度体积源表面的声散射作用会导致壳体内部声场结构发生改变,内声场声腔共振峰发生偏移,并且在部分频段引起较强的声透射现象;此外,体积源指向性变化对壳体内外声场强弱影响较小,其显著作用表现在改变了外辐射声场的远场指向性.该研究结果对噪声预报和控制有一定的参考价值.

Sound radiation from finite cylindrical shell excited by inner finite-size sources

The study of the characteristics of noise sources in cylindrical shells is the foundation of sound field prediction. Although noise sources are usually regarded as point sources to simplify the calculation model in noise source localization and waveguide sound propagation, the approximation is limited to far-field problems. For the near-field acoustics problems in engine room and ship cabin, the radiated noise possesses the spatial directivity because of the complex vibration distribution of the noise source surface. Moreover, the sound scattering on the surface of finite-size sources makes the noise source itself act not only as the energy input of sound field, but also as the scatterer to change the structure of sound field in the environment. These factors lead to large errors when the finite-size source is simplified into a point source. In order to explore the influence of finite-size source on the acoustic field inside and outside the underwater vehicle structure, the shell coupled equation is constructed by combining thin shell theory, equivalent source and Green function. The effects of source surface scattering and directivity on the acoustic field inside and outside the cylindrical shell are studied. The results show that the accuracy of finite-size source construction is related to the equivalent source location. It proves that equivalent source allocation should be arranged in the middle of the geometric center of sources and its structural surface. Sound scattering from the surface of the finite-size source will change the sound field inside the shell, and then the resonant peaks of the cavity are shifted to the high frequencies as the source volume increases, which causes a strong sound transmission phenomenon in some frequency bands. In addition, the directivity of the finite-size source has little effect on the intensity of the sound field inside and outside the shell, which is evident in changing the far-field directivity of the radiated sound field. The research results are valuable for noise prediction and noise control.