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

To investigate the influences of interference between the fuselage/propeller on the aerodynamic and aeroacoustic 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 domain and the other solid object. Then the Computational Fluid Dynamics (CFD) method based on the Unsteady Reynolds Averaged Navier-Stockes (URANS) equations was established for the simulation of helicopter fuselage/propeller flowfield. Furthermore, the methods based on the Ffowcs Williams 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.