Computational research on aerodynamic forces of scissors tail-rotor in forward flight based on the N-S equations

A numerical method is developed to calculate the aerodynamic forces of scissors tail-rotor in forward flight. In the present method, the three dimensional unsteady Navier-Stokes equations are used as control equations, which are discretized by low dissipation Roe scheme and implicit LU-SGS scheme in space and time directions respectively. Besides, the dual-time stepping method is employed to simulate the unsteady phenomenon of the scissors tai-rotor in forward flight, and moving embedded grid technology is applied to account for rigid blade motion in rotation. Based on the present method, calculations on the aerodynamic performance for the Lynx helicopter tail-rotor in hover are firstly performed to show the capability of the present model in predicting aerodynamic performance of the tail-rotor. Then, simulations for the aerodynamic loads of Helishape 7A rotor are conducted to verify the effectiveness of the numerical method in calculating the aerodynamic forces for forward flight rotors. Meanwhile, calculations on the aerodynamic forces for the scissors tail-rotor in forward flight are performed, and the effects of configuration parameters on the aerodynamic force of scissors rotor are analyzed. The calculated results indicate that, in forward flight, the average thrust of scissors tail-rotor is higher than that of the conventional one with the same blade pitch, and the scissors tail-rotor will suffer more serious BVI than the conventional one in the azimuthal angle range of 90°-180°-270°.