三段翼型气动噪声特性数值分析

Numerical analysis of the aerodynamic noise characteristics of a three-element airfoil

采用混合计算气动声学方法对某三段翼气动噪声特性进行分析,气动声源采用IDDES方法模拟,噪声传播预估采用Curle方程。利用圆柱-NACA0012翼型绕流算例对数值算法进行验证,近场气动声源与远场气动噪声的预测结果和实验相吻合,IDDES方法可以精细捕捉涡脱落、分离和再附着等非定常流动现象,能为气动噪声的预测提供足够精确的声源信息;采用Curle方程能够准确高效地预测远场气动噪声,对低马赫数流动可以忽略四极子声源对远场的贡献。在此基础上,对来流迎角7.5°、马赫数0.17和雷诺数1.71×10^(6)的某三段翼气动特性和噪声特性进行预测,结果表明:襟翼表面脉动压力对噪声贡献最大,缝翼表面脉动压力对噪声贡献最小;1 000 Hz附近的低频噪声源于襟翼尾缘剪切层流动分离和尾涡脱落;缝翼凹腔内的涡脱落、融合和撞击主要诱发500 Hz以下的低频噪声;襟翼尾涡脱落和主翼后缘下方流动分离则产生4 500 Hz附近中频噪声。

A hybrid computational aeroacoustics technique was performed to investigate the aerodynamic noise characteristics of a three-element airfoil.The aerodynamic source was simulated with an improved delayed detached eddy simulation(IDDES) method and the far-field aerodynamic noise was computed by Curle’s equation.The noise generated by a low Mach number flow past the rod-airfoil configuration was evaluated by the numerical approach and compared with the experimental data.The comparison shows that IDDES method can accurately describe the flow characteristics including the vortex shedding,detachment and reattachment,and provide detailed sources for the prediction of the acoustic far-field.The Curle’s equation can evaluate the far-field noise accurately and efficiently.The quadrupole source can be neglected for the acoustic far-field of a low Mach number flow.Therefore,the aeroacoustics and aerodynamics characteristics of the three-element airfoil at Reynolds number of 1.71×10^(6),Mach number 0.17 and angle of attack 7.5° were analyzed.The pressure fluctuation on the surface of the flap exerts largest influence on the acoustic far-field while the slat exerts minimum.The peak values of the noise near 1 000 Hz are generated by the shear layer flow separation and the vortex shedding at the trailing edge of the flap.The vortex shedding,fusion and collision in the slat cove mainly induce noise below 500 Hz.The noises near 4 500 Hz are resulted from the vortex shedding at the trailing edge of the flap and the flow separation at the trailing edge of the main wing suction surface.