非均匀流场中螺旋桨线谱噪声指向性分析

Directivity Prediction on Tone Noise of Propeller Operating in Non-Uniform Flows

为了对非均匀流场中螺旋桨线谱噪声的指向性特征进行分析,在Ffowcs William-Hawkings方程的基础上,建立了非均匀流场中螺旋桨线谱噪声的频域预报理论,该理论可对声源在真实桨叶表面进行积分。讨论了螺旋桨叶数、来流谐波阶数以及叶片表面力对线谱噪声指向性的影响。结果表明,特征耦合系数是线谱噪声指向性分布形态的决定因素,并且当特征耦合系数等于零时,辐射噪声主要由轴向力和主要谐波所贡献;当特征耦合系数不为零时,轴向力和主要谐波的贡献只集中于桨轴方向,而桨盘面处的噪声贡献则来源于周向力和与叶片数目相等的谐波。

In order to analyze the directivity performance of tone noise of propeller operating in a nonuniform flow,a numerical model,based on Ffowcs William-Hawkings equation,for predicting far-field propeller noise due to non-uniform flows is proposed which requires the aerodynamic sources to be integrated over the actual blade surface.The influence of blade number,inflow harmonic and unsteady blade forces on the directivity of radiated tone noise are discussed,which shows that the characteristics coupling factor between inflow harmonic and the rotating blades play important roles in the directivity feature.When the characteristic coupling factor equals to zero,the total radiated noise is mainly created by the axial force and the main inflow harmonic,while for the characteristic coupling factor not equals to zero,however,the noise contribution due to the axial force and the main inflow harmonic only dominate near the propeller axis,while the tangential force and the inflow harmonic that equals to the blade number dominate in the direction vertical to the propeller axis.