STUDIES ON VORTEX INTERACTION MECHANISM AND AERODYNAMIC CHARACTERISTIC OF SCISSORS TAIL ROTOR

The design of the unconventional scissors tail rotor has a powerful influence on the overall aerodynamic performance of helicopter, and the aerodynamic interaction mechanism of the unconventional tail rotor has been investigated due to its complexity. To get the interaction mechanism and aerodynamic characteristic of scissors tail rotor, a numerical method based on computational fluid dynamics (CFD) technique is established to simulate the vortex flowfield of scissors tail rotor in hover. Based on the embedded grid system, a CFD simulation method is developed by solving the compressible Reynolds-averaged Navier-Stokes (RANS) equations. Based on the validation of the CFD method, the evolution laws of position and strength of blade-tip vortex for two different scissors tail rotors are obtained by quantitative analysis in hover. Thus, close vortex-surface interactions, impingement and burst motions in the process of blade-vortex interaction are analyzed in detail, also the interaction and mergence process among the different scales vortex has been captured accurately. Furthermore, the influences of the two configuration parameters (scissors angle and vertical space) on their aerodynamic characteristics have been analyzed in hover. The simulated results demonstrate that the flowfield of the scissors tail rotor is very complicated due to various blade-vortex and vortex-vortex interaction. In addition, the configuration parameters of scissors tail rotor have important effects on its aerodynamic characteristics, and configuration L shows more advantages of improving the aerodynamic performance than configuration U has.