中低雷诺数翼型气动噪声特征及机理研究

本研究在中低雷诺数（Re=2.0×105）下，对NACA 0012翼型从零攻角到后失速工况的远场噪声特征及翼型前缘与尾缘处的流场特征进行了分析。通过研究PIV（粒子图像测速系统）可视化流场特征及其与远场噪声的关联性，探索了从附着流动到失速流动状态的翼型气动噪声机理。对不同攻角下的翼型流场特征与远场噪声特征频谱进行对比分析发现，翼型在有效攻角0°即流场对称时存在明显的
纯音噪声，翼型压力侧与吸力侧周期性流动对纯音噪声均有贡献。在低攻角下，有效攻角为2°- 8°时即流场呈非对称流动状态，翼型纯音噪声主要由压力侧周期性流动贡献。在翼型进入失速状态前后，翼型上纯音噪声逐渐消失，前缘和尾缘处附近湍流流动没有观察到周期性流动特征。

The far field noise characteristics of NACA 0012 airfoil from zero to stall Angle and the flow field characteristics at the leading edge and trailing edge of the airfoil were studied in this research. By analyzing the
characteristics of visual flow field of PIV (particle image velocimetry system) and its correlation with far-field noise, the aerodynamic noise mechanism of airfoil from attached flow to stall flow state is explored. The spectrum of flow field characteristics of airfoils at different angles of attack at inflow velocity of 10 m/s is compared with that of far-field noise. It is found that airfoils with an effective Angle of attack of 0°, i.e. a symmetrical flow field, have obvious pure sound noise, and both the periodic flow at the pressure side and suction side of airfoils contribute to pure sound noise. When the effective angle of attack is 2° -8°, the flow field features an asymmetric flow state, and the pure tone noise of the airfoil is mainly contributed by the periodic flow at the pressure side. Before and after the airfoil entered the stall state, the tonal noise on the airfoil gradually disappeared, and no periodic flow characteristics were observed in the turbulent flow near the leading edge and trailing edge.