大侧斜螺旋桨负载噪声的边界元数值声学方法频域内计算分析

摘要

为探索艇尾桨无空化水下辅射噪声的数值预报方法,采用流场大涡模拟(LES)和声场边界元数值声学的弱耦合方法在频域内对艇尾标称伴流条件下的大侧斜螺旋桨水下负载噪声进行了预报.耦合方法的可信性由计算得到的DTRC4119无侧斜螺旋桨球面空间声压分布和特征测点处声压频谱级曲线与文献[5 -6]计算值的比较给予了验证.LES计算时选用动力学SmagorinskyLilly亚格子应力模型(DSM),负载声压场由桨叶及桨毂表面所形成封闭面的压力分布和法向速度分布决定.声源节点和声节点变量采用一对一的变量守恒传递方式.结果表明:定常雷诺时均(RANS)模拟计算2个桨的推力和力矩系数均与敞水试验值吻合良好,以此作为LES模拟的流场初值是可信的；LES非定常解均能准确地捕捉2个桨桨叶叶梢处叶频和倍叶频以及尾流中弱轴频信息；计算得到的DTRC4119螺旋桨在200 Hz内总声压级为126.4 dB,大侧斜螺旋桨在0～l kHz频带内总声级为116 dB.为艇尾桨水下噪声预报探索了一条新的途径.%For numerical prediction of non-cavitation underwater radiated noise of propeller behind submarine, a highly-skewed propeller's underwater load noise in nominal wake flow is predicted by using large eddy simulation (LES) and boundary element numerical acoustic weak-coupling method in frequency domain. This coupling method is verified by comparing the calculated sound pressure directivity characteristics on the 3 D spherical surface and downstream axial measured point' s broadband sound pressure spectrum of DTRC4119 propeller with calculation results provided by the literature[5 -6] in the same conditions. A dynamic Smagorinsky-Lilly subgrid-scale stress model ( DSM) is used in the unsteady field LES calculation. Then, the sound pressure field is determined solely by the pressure distribution and normal velocity distribution on the closed surface formed by blades and hub surfaces after nodes conservative transfer of the acoustic sources nodal to the acoustic grid. The predicted results show that both propeller's thrust and torque coefficients obtained by RANS simulation are fit very well with the experiment data,which verify the input flow field to the LES simulation. LES unsteady calculation can present precisely two propeller's blade passing frequency (BPF) , their harmonics and wake weak axis passing frequency ( APF) information too. The calculated total sound pressure level of the DTRC4119 propeller below 200 Hz is 126. 4 dB, while the total sound pressure level of the highly-skewed propeller in 0 ~ 1 kHz is 116 dB, thus providing a new method to measure the propeller noise behind submarine in the ship.