艇后大侧斜螺旋桨负载噪声数值分析

为研究艇后非均匀流场中大侧斜螺旋桨无空泡负载噪声的分布规律，文章采用“CFD+BEM”法，以SUBOFF潜艇后某大侧斜桨为研究对象，首先稳态计算均匀进流下螺旋桨敞水特性，模拟系数值与实验误差在3%以内，验证了CFD数值计算的可信性。然后采用大涡（LES）模拟，对“艇+桨”进行三维非定常数值模拟，计算得到桨表面声偶极子数据后，通过距离加权平均法映射到声网格节点上，将噪声源直接分布在桨叶表面上进行积分来预报螺旋桨的低频线谱噪声。采用边界元法基于扇声源理论通过FW-H声类比方程分别在1 kHz以内对桨盘面、轴向纵剖面及10倍桨半径球场的噪声进行频域求解。研究表明：桨盘面和轴向纵剖面上声指向均呈8字形，但受螺旋桨自身旋转及大侧斜的存在，指向性不唯一；球场声场显示，轴向声辐射面较大，声辐射强，径向辐射面小且辐射较弱；特征点的计算结果显示，高阶叶频声压级明显比一阶叶频低，这与物理现象相符，将特征点处结果与已发表文献进行对比，吻合性良好，并对存在的差异作出了合理的物理解释。该文为螺旋桨噪声预报介绍了一种可行的新方法。

Numerical Analysis of Load-noise of a Highly-skewed Propeller behind Submarine

This investigation combined the Computational Fluid Dynamics (CFD) with Boundary Ele-ment Method(BEM) to predict the load noise of a highly-skewed propellers behind submarine (SUB-OFF) with full appendages. The credibility of CFD was validated by comparing the results derived from steady simulation of the open water propeller with experiment data. The unsteady loading (dipole sound source) on blade surface was calculated by transient simulation of the same propeller fixed after sub-marine and then was transferred to the sound grid. The integration of the noise source was performed over the true blade surface, which was used to predict the propeller’s low-order blade frequency noise below 1 kHz. The BEM method was used to solve the FW-H equation to get the sound pressure direc-tivity characteristics on the 3D spherical surface enclosed the propeller as well as two planes in the surface of the propeller disc and its perpendicular surface based on theory of acoustic fan source, total sound pressure level on the downstream axial measured points were also calculated. Study shows that the sound pressure directivity on both the propeller disc and its perpendicular plane presented as ‘8’, but the directivity is not unique because of the existence of rotation and skew angle of the propeller. The 3D spherical field showed that the radiant surface in the direction of the propeller disc was smaller and radiated weaker than its perpendicular plane. The results of the typical points showed that the 1st order blade frequency SPL exceeded the high-order blade frequency SPL obviously, which accorded well with fact. A good consistency had gotten after comparing with the published literature and reasonable explanation was also given to the difference. Thus, this paper introduced a new method to measure the propeller noise behind submarine in the ship effectively.