Numerical analyses of aeroacoustic characteristics of tiltrotor considering the aerodynamic interaction by the fuselage in hover

Abstract

Numerical investigations are performed to investigate the interaction effect between the rotor and fuselage on the aerodynamic and aeroacoustic characteristics of the XV-15 tiltrotor during hovering flight. A hybrid method, which combines a Computational Fluid Dynamics (CFD) solver and an aeroacoustics simulation code, has been developed in order to accurately capture the complex interaction flowfield and acoustic pressure of the tiltrotor. To simulate the interaction of the fuselage on the aeroacoustic source of the rotor, a CFD solver based on a sliding mesh algorithm and unsteady Reynolds-Averaged Navier-Stokes equations is utilized. Additionally, to enhance the accuracy of the interaction simulation, the Lower-Upper Symmetric Gauss-Seidel (LU-SGS) method is adopted. A specialized code, based on the Ffowcs Williams-Hawkings (FW-H) equations and propagation time, is developed to simulate the rotor noise. Then, the numerical investigation on the aerodynamic and aeroacoustic interaction between a full-scale tiltrotor and fuselage (including the wing) is conducted. In addition, the study explores various tiltrotor configurations to analyze mechanisms for suppressing interaction noise. The results indicate that the aerodynamic loading of tiltrotor fluctuates severely interacted with the fuselage. This, in turn, causes an increase in noise by approximately 5 dB. What's more, decreasing the fountain effect would have a positive effect on reducing the range of variation in loading, and it could ultimately suppress the interaction noise.