关键词: 侧风环境, 尾桨涡环, 尾桨抗侧风, 翼型优化, 全湍流伴随

Abstract:

The tail rotor vortex ring seriously endangers the flight safety of helicopters. To explore the influence of the vortex ring on the induced velocity field near the rotor disk and explain the cause of unsteady pulsation of blade thrust， we construct a set of numerical calculation methods for the tail rotor vortex ring based on unsteady Reynolds averaged Navier Stokes equations， and conduct aerodynamic analysis combining the blade element theory and the circular vortex ring model. Meanwhile， an airfoil optimization framework with the continuous adjoint turbulence is established to solve the inherent defects of the frozen eddy viscosity assumption， and the obtained airfoil is used in the design of tail rotors to improve the crosswind counteraction ability. The results show that the induced velocity field near the propeller disk is sensitive to the inlet velocity of the cross wind. In the typical vortex ring state， the cross wind of 14.65 m/s causes the vortex strength of the vortex ring to increase and change continuously， induces decrease and dynamic change of the effective angle of attack of the blade section， and further reduces the tail rotor thrust to 58.5% of the original value with high-frequency pulsation. The adjoint turbulence method is superior to the frozen eddy viscosity assumption in terms of optimization convergence. Compared with those of the base tail rotor， the thrust of the tail rotor obtained by optimizing the airfoil and the figure of merit are increased by 10.9% and 3.9%， respectively， and the critical crosswind velocity of the tail rotor entering the vortex ring is expanded.

Key words: crosswind environment, tail rotor vortex ring, tail rotor counteract crosswind, airfoil optimization, adjoint turbulence