舰船螺旋桨空化低频辐射噪声时频域仿真

Waveform simulation of low frequency line spectrum on nearfield radiated propeller cavitation noise

依据空泡动力学经典理论的分析结果,仿真出单个空泡体积变化时间波形及相应的声脉冲。将旋转桨叶充分空化情况下,一周期内引起的空泡群破灭过程的平均行为用单空泡仿真,并将不均匀尾流场空泡群噪声辐射近似描述为以叶片频倒数为周期间隔出现、幅度随机变化的单脉冲所构成的脉冲序列组成,并在声压脉冲波形上叠加适当的高斯白噪声。推导了宽带洛埃镜模型信道响应函数,分析其相应的谱特性,对深海近表面目标螺旋桨空化近场低频辐射噪声场进行了仿真,仿真结果与实测数据吻合较好。

The waveform of a single cavity volume change based on classical single cavitation dynamics model has been simulated.The instantaneous free-field acoustic pressure radiated from a pulsating monopole source can be derived by solving the acoustic wave equation in the case of a fluctuating mass source.If its density change is assumed to be negli-gible,the monopole pressure waveform is directly proportional to the second derivative of the cavity volume change.Based on the physical mechanism of low frequency line spectrum on propeller cavitation noise,the acoustic radiations of a great of cavitation bubbles can be represented by a single cavitation bubble during the time of propeller cavitation.A pulsating radiated acoustic pressure,which is caused by propeller rotation,is treated as a pulsatory random process with the radiated acoustic pressure waveform from a single cavity,equal iterative,random amplitude and structure of group by group.Through overlapping white Gaussian noise,the randomicity of pressure waveform of low frequency line spectrum is simulated.The transfer function expressions of radiated acoustic pressure field based broadband Lloyd-Mirror pattern are deduced,and the characteristic of transfer function is analyzed.Based on the above,the near-field radiated acoustic pressure in deep water from a shallow pulsating monopole source is simulated.Although the model of low frequency line spectrum on propeller cavitation noise is simplified,the results are in good agreement with experiment results.