螺旋桨激励水下壳体振动噪声数值研究

为真实模拟壳体噪声的激励源特性,建立螺旋桨-轴系-壳体耦合系统有限元模型,以CFD计算得到的螺旋桨非定常载荷作为激励源,采用模态叠加法计算耦合系统强迫振动响应;分别以桨叶表面偶极子声源和耦合系统表面振速作为边界条件,采用声学直接边界元法计算螺旋桨直接辐射噪声和耦合系统振动噪声。数值计算结果表明:两种噪声的声压级都随螺旋桨转速的增加而增大,其中振动噪声增幅较小;耦合系统振动噪声声压级随轴承刚度的增加而增大;两种噪声的声压级在量级上较为接近,在频谱及声压分布上具有各自的特征,在预报耦合系统水下辐射噪声时应综合考虑两种噪声的影响。

Numerical study on the propeller induced vibration noise of an underwater hull

To simulate the excitation source characteristics of a hull’s noise with reality, the finite element model of a propeller-shaft-hull coupled systemwas established, and forced vibration responses of the coupled system were calculated using the mode superposition method taking an unsteady load of propeller calculated by CFD as an excitation source.The propeller’s direct radiated noise and coupled system’s vibration noise were calculated with the acoustical direct boundary element method using the surface dipole of the blade and the surface vibration velocity of the coupled system as a boundary condition parameter respectively.The numerical results show that: the sound pressure level(SPL) of the two noises increases with the increase of propeller rotating speed, and the vibration noise’s growing rate is relatively small; the SPL of coupled system’svibration noise increases with the bearing stiffness; the SPL of the two noises has the same order of magnitude and different specialties in frequency spectrum and sound pressure distribution, and it is required to take their influences into account when predicting the coupled system’s underwater radiated noise.