Computation on aerodynamic and aeroacoustic characteristics of scissor tail-rotor under sideslip condition

In view of the complex aerodynamic environment and noise characteristics of the scissors tail rotor under the condition of sideslip, an aeroacoustic prediction method was proposed based on computational fluid dynamics (CFD)/FW-H equation. Firstly, the flow field of the scissor tail-rotor was numerically simulated by solving the Reynolds averaged Navier-Stokes (RANS) equation. Then, the FW-H equation based on the integral surface of the solid surface was used to solve the aeroacoustic. Under sideslip circumstances, the aerodynamic and aeroacoustic properties of the standard tail rotor and the scissor tail rotor (L45) were examined. The numerical results show that with the increase of sideslip angle, the thrust fluctuation of the scissor tail-rotor increased more than that of the conventional tail-rotor. Under the same condition, the thrust fluctuation of a scissor tail-rotor is obviously larger than that of a conventional tail-rotor, which is generally more than 2 times. Therefore, the design should adequately account for the detrimental effects of the scissors tail rotor on the helicopter’s balance and control. In most states, the maximum total noise of a scissors tail-rotor is bigger than that of a conventional tail-rotor.