高速直升机机身干扰对推力桨气动与噪声源特性的影响

Interferences of high-speed helicopter fuselage on aerodynamic and aeroacoustic source characteristics of propeller

研究高速直升机前飞时机身/后置推力桨的气动干扰对其气动与噪声源特性的影响。构建了一套适用于机身/推力桨流场模拟的高鲁棒性网格系统,贴体网格采用机身非结构/桨叶结构的混合网格,各贴体网格分别与背景网格建立嵌套关系,提出了网格外边界自适应实体物面的边界识别方法以规避贴体网格计算域与实体的重合问题。基于URANS(Unsteady Reynolds Averaged Navier-Stockes)方程构建了一套高速直升机机身/推力桨干扰流场的模拟方法,并基于FW-H(Ffowcs Williams and Hawkings)方程进一步建立了机身/推力桨噪声预估方法。通过与ROBIN机身/旋翼干扰试验数据、AH-1G旋翼噪声试验数据进行对比,验证了分析方法的有效性。开展了高速飞行状态下机身/推力桨干扰流场的高精度数值模拟,重点分析了机身/推力桨流场的干扰机制,综合对比了有/无机身干扰的推力桨气动噪声源特性。结果表明:在机身干扰下,推力桨整体推力会出现小幅度的波动,波动幅度约5.34%。与孤立推力桨比较,受干扰的推力桨在中/高桨盘夹角方向上的噪声声压级(SPL)大幅增大,且增大幅值与前进比正相关。此外,机身表面压力的波动会诱发载荷噪声,进一步改变了总噪声的频域特性。

To investigate the influences of interference between the fuselage/propeller on the aerodynamic and aero-acoustic source characteristics in high-speed,firstly,a highly-robust embedded grid method was established in which hybrid grids of fuselage non-structure/propeller structure were adopted.An outer boundary identification method was proposed by adapting the outer boundary to the solid object so as to circumvent the space overlap between the grid do-main and the other solid object.Then the Computational Fluid Dynamics(CFD)method based on the Unsteady Reyn-olds Averaged Navier-Stockes(URANS)equations was established for the simulation of helicopter fuselage/propeller flowfield.Furthermore,the methods based on the Ffowcs Wiliams and Hawkings(FW-H)equations were applied for fuselage and propeller noise prediction.The effectiveness of the developed method was verified by comparing the simulation results with the results of the NASA ROBIN/rotor experiment and the AH-1G noise experiment.Finally,the flowfield of the fuselage/propeller was simulated for the analysis on the interference mechanisms and aeroacoustics characteristics,and some meaningful conclusions were obtained.Under the interference of the fuselage,a fluctuation of about 5.34%occurred on the propeller thrust while the fluctuation of the single blade thrust was more significant.The Sound Pressure Level(SPL)of the propeller under interferences increased significantly(compared to the isolated propeller).The increased values were positively correlated with the advance ratio.In addition,the frequency domain characteristics of the total noise were altered due to the loading noise induced by the fluctuation of fuselage surface pressure.