直升机旋翼桨-涡干扰脉冲噪声传播特性研究

建立了一个基于Navier-Stokes方程和自由尾迹模型的高效耦合CFD方法,用于旋翼桨-涡干扰气动和噪声特性的研究。该方法将旋翼流场计算域分为两部分:在桨叶附近区域,通过求解Navier-Stokes方程来模拟流场中旋翼桨尖涡的形成;在尾迹输运区,采用自由尾迹模型表示尾迹涡的运动及其影响。噪声的计算采用基于声学类比法的FW-H方程。应用上述方法对AH-1/OLS旋翼桨-涡干扰状态进行了计算,通过对比脉冲噪声的声压时间历程,验证了方法的有效性。在此基础上,对桨-涡干扰噪声的空间传播特性进行了研究。计算结果表明:下降飞行状态的旋翼,在桨盘面会产生多处桨-涡干扰现象,桨叶片数增多,干扰也会明显增加;桨-涡干扰噪声具有较强的方向性,指向旋翼前行侧的前下方,其噪声声压级的衰减速率与距离成线性反比关系。

Propagation Characteristics of Helicopter Rotor Blade-Vortex Interaction Noise

A hybrid method based on Navier-Stokes equation and free wake analysis is deveLoped for studying the aerodynamic and acoustic characteristics of rotor blade-vortex interaction (BVI). In this method, the flow field is divided into two zones, a Navier-Stokes code is used to model the tip vortex formation around the blade, while a free wake model is employed in vortex transport area, to account for the effect of the far wake. The noise prediction is based on the well-known FW-H equation. By this developed method, the aerodynamic loading and acoustic calculations are performed for the AH-1/OLS rotor in the BVI condition. The present method is validated by comparison of the pressure time history with the available experimental data. Furthermore, the BVI noise propagation characteristic is studied. The results indicate that, the BVI phenomena will occur at several azimuthal angles on the rotor in the descent flight condition. With more blades, the number of interactions is markedly increased. The noise has strong directivity, and radiates toward the low and front of blades on the advancing side. The sound pressure level of BVI noise has linearly inverse relationship with observer distance.