湍流激励下柔性层贴敷加筋板自噪声的特征机理

The characteristics and mechanisms of turbulent pressure induced self-noise of the elastomer layer attached stiffened plate

为了研究湍流激励下柔性层贴敷加筋板自噪声的特征机理,基于湍流边界层壁面脉动压力功率谱模型、周期加筋板弯曲运动方程和固体波动方程以及力平衡与位移连续边界条件,建立了湍流边界层壁面脉动压力激励下柔性层贴敷单向周期加筋板的振动及内噪声物理模型。研究发现:橡胶外贴时对湍流激励下壳板的减振降噪主要依靠橡胶的厚度模态振动。无筋时,橡胶层外贴板较无橡胶贴敷板,主要降低湍流脉动压力的水动力学成分所致结构自噪声,距壳板0.05m时,声压降幅小于3 dB,橡胶外贴加筋板相对于加筋板,对湍流激励结构自噪声的降低基本涵盖整个波数域,距壳板0.7 m处,声压降幅仍然在20 dB左右。肋骨横截面高度或宽度每增大1倍,壳板肋骨处加速度自功率谱级降低3 dB,非肋骨处加速度及板内侧声压自功率谱则基本不变,肋骨间距改变对壳板加速度响应及板内侧声压自功率谱级皆无显著影响。

In order to study the characteristics and mechanisms of turbulent pressure induced self-noise of the elastomer layer attached stiffened plate,the elastomer layer attached periodically stiffened plate model induced by turbulent fluctuating pressure was established based on turbulent wall pressure fluctuation spectrum model,periodically stiffened plate flexural motion equation,three-dimensional solid wave equation as well as force equilibrium and displacement continuity conditions.The study indicates:the noise reduction of self-noise of the turbulent induced elastomer attached plate mainly attributes to the thickness mode vibration of the rubber layer.In comparison with the original plate,external elastomer attached plate mainly decrease the structure self-noise caused by hydrodynamic component of turbulent pressure fluctuation,while the distance between the plate and the observation point reaches as long as 0.05 m,the reduction amplitudes of sound pressure decreases to less than 3 dB.Compared with stiffened plate,external elastomer attached stiffened plate possesses lower turbulent pressure induced structure self-noise over all wavenumber domain,while the distance between the plate and the observation point reaches as long as 0.7 m,the reduction amplitudes of sound pressure are still around 20 dB.While stringer cross section height or width becomes twice larger,the acceleration auto-spectra level of shell plate at stiffeners decreases by 3 dB,however its counterparts at other places do not variate.Basically for all positions on the plate,the variation of stringer distance has no apparent influence on the shell structure self-noise auto-spectra level.