周期加肋夹芯透声窗的声呐自噪声特性研究

An Investigation of Sonar Self Noise for Periodically Stiffened Sandwich Acoustic Window

以舰船声呐罩透声窗的低噪声设计为背景,针对周期加肋夹芯平板和平行腔体组成的简化声呐罩模型,采用Fourier变换方法和功率谱密度函数,建立加肋夹芯透声窗受平稳随机湍流脉动压力激励产生的声呐部位水动力自噪声的计算方法,数值计算肋骨几何尺寸和间距等参数对声呐自噪声的影响。研究结果表明加肋透声窗在湍流脉动压力激励下产生的声呐自噪声,取决于声呐罩的空间滤波特性。肋骨引起的波数迁移,使透声窗与湍流脉动压力的传输峰值分量发生空间吻合共振,明显增大声呐自噪声。加肋夹芯透声窗的弹性波传播截止效应,部分抵消肋骨产生的空间调制效应,可降低声呐自噪声5 dB^10 dB。

Aimed at the low noise design of sonar dome in ships, a methed is presented for calculating the hydrodynamic component of sonar self noise in a simplied sonar dome consisting of periodically stiffened sandwich acoustic window and parallel acoustic cavity, which is excited by stationary random fluctuation pressure of turbulence boundary layer, using spatial FOURIER transform and the wavenumber-frequency spectrum analysis. The influence of geometrical parameters and distance of ribs in the stiffened sandwich acoustic window on the sonar self noise is analyzed numerically. The resuits show that the sonar self noise for the case of stiffened acoustic window excited by the fluctuation pressure under turbulence boundary layer depends on the spatial filtering of sonar dome. When the wavenumber response peak of the sonar dome coincides with the convective peak of the wavenumberfrequncy spectrum of the fluctuation pressure under turbulence boundary layer because of the wavenumber transfer caused by scattering mechanism of ribs, the sonar self noise obviously increases. But the cut-off effects of elastic wave propagating in the visco-elastic layer of stiffened sandwich acoustic window partly compensate spatial modulation effect of the ribs, so that the sonar self noise would decrease 5dB-10dB.