剪刀式尾桨前飞状态气动噪声特性计算

基于计算流体力学（CFD）建立了适用于剪刀式尾桨的流场计算模型，采用嵌套网格方法模拟尾桨运动，采用双时间方法进行时间推进。针对不同的尾桨构型，采用高效配平策略“差量法”将剪刀式尾桨配平至相同负载状态。在此基础上，采用Ffowcs Williams-Hawkings（FW-H）方程计算剪刀式尾桨的气动噪声特性。应用该方法对不同前飞速度下剪刀式尾桨的气动力和噪声进行计算分析，着重研究了剪刀角和轴向间距两个重要构型参数的影响。计算结果表明:剪刀角对剪刀式尾桨气动力和气动噪声特性均有重要影响，而轴向间距在合理的变化范围内，对尾桨影响较小。与常规尾桨相比，前飞状态下剪刀式尾桨的噪声指向性变化较小，但噪声幅值变化显著。 

Computation on aeroacoustic characteristics of scissors tail-rotor in forward flight

A flow field calculation model for scissors tail-rotor was established based on the computational fluid dynamics (CFD). The nested grid method was used to simulate the blade motion, and the dual-time method was used for time propulsion. A high-efficiency trim strategy based on the “delta method” was adopted to trim the collective pitch for the scissors tail-rotor. On the basis, the aeroacoustic characteristics of the scissors tail-rotor were calculated by using Ffowcs Williams-Hawkings (FW-H) equation. This method was applied to the calculation of scissors tail-rotor (L configuration and U configuration) in different forward velocities. The effects of the scissors angle and vertical space on the aerodynamic force and noise of scissors tail-rotor were compared and analyzed. It was found that the scissors angle had an important effect on aerodynamic force and noise characteristics of the scissor tail rotor, while the vertical space had little effect on the tail rotor within a reasonable range. Compared with the conventional tail rotor, the noise directivity of the scissor tail rotor changed little in forward flight, but the noise amplitude changed significantly.