舰艇螺旋桨水下噪声预测

摘要

Cavitation noise of marine propellers is an important component of the ship's radiating underwater sound. Given the flat-slope characteristic of the source spectrum level of propeller noise, the spectrum decay index is presented,and the dependent parameters of the peak frequency and its spectral peak are analyzed at the same time.The cavitation noise spectrum formulations within part frequency band for the two special speed under propeller cavitation condition can be used to construct ship's propeller cavitation noise spectra at any speed by linear regression. Uniting the function of spectrum level at the given frequency versus propeller diameter under a given tip circumferential velocity condition and the increment of the spectrum level at the given frequency due to the change of tip circumferential velocity at some frequency,the spectrum level at the given frequency under non-cavitation can be derived for submarine,while the sound level increment on account of spectral level getting into the sharp spectral peak regime and the additional increase of rotating speed above the critical valve should be added under the cavitation condition,in which case the submarine propeller noise spectrum can be predicted at any speed within the whole band. Finally, the derived equations are validated by the exist data and the error is less than 4dB. The tip cavitation inception index used during the prediction and the existence of narrow band tonal noise should be determined by the cavitation tunnel experiment.%螺旋桨空化噪声是舰艇最主要的辐射噪声源.文章分析了螺旋桨噪声平坡形谱曲线的特点,给出源声级谱级曲线的衰减指数值,分析了特征频率和峰值谱级的影响因素.由螺旋桨空化状态下两个特征航速对应的部分频段内的噪声谱级计算式拟合得到水面舰船螺旋桨空化后任意可达航速下的噪声谱曲线.结合叶梢周向速度一定时特征频率处谱级与螺旋桨直径的函数关系和频率一定时叶梢周向速度变化引起的特征频率处谱级变化量,得到潜艇螺旋桨无空化状态下特征频率处谱级,在空化状态下,还需要加上螺旋桨进入尖锐谱峰区和转速进一步升高引起的声级增加量,从而得到了潜艇在任意航态下整个频带内螺旋桨噪声谱级的计算式.利用已有数据对计算式进行了检验,计算声级误差小于4dB.计算中用到的叶梢初生空泡数和判定是否出现窄带调噪声要通过空泡筒试验确定.