Gurney襟翼对机翼地面效应气动特性和流动结构的影响实验研究

The experimental study of aerodynamics and flow structures of a wing with Gurney flaps in ground effect

介绍了加装Gurney襟翼的NACA0012机翼在地面效应下的升/阻力、翼尖涡和尾流场的风洞实验结果,以探讨其气动特性与流场结构之间的相关性。结果表明,加装Gurney襟翼后,与自由空间机翼相比,在相同攻角下地效机翼升力增加明显。与净NACA0012机翼相比,Gurney机翼阻力会显著增加,从而导致在约2°以上攻角时升阻比小于NACA0012机翼,但机翼升阻比变化没有明显的峰值和升降趋势,表明机翼的纵向稳定性得到改善。在地效的作用下,翼尖涡强度被抑制,而且会向机翼外侧偏移,从而降低了诱导速度,引起机翼升/阻力的变化;此外,采用PIV技术,观察到了Gurney襟翼周围的速度场在地面效应下的分布状态。

An experimental study on the lift/drag forces, tip vortices and wake flow of a NACA0012 wing with Gurney flaps（GF） in ground effect is introduced. The goal of the study is to investigate the influence of the flow structure on the aerodynamics of the wing in ground effect. The experiment was carried out in a wind tunnel, the Reynolds number is 8 X 104 based upon^the chord length of the wing. The lift/drag forces are measured on conditions of various ground heights and angles of attack. The velocity distributions of tip vortices are measured by a 7-holes probe scanning. The results show that the lift force of the Gurney flaps in- creases significantly compared with that of a wing in free space at same angel of attack. Compared with that of a clean NACA0012 wing, the drag force of a wing with Gurney flap increases as well, leading to the de- creasing of the lift-to-drag ratios of the Gurney flap than that of a clean wing, when the angle of attack is lar- ger than 2~. However, an easy curve of the lift-to-drag ratios to the angle of attack without obvious peak val- ue is observed, which implies the pitch stiffness of the wing with Gurney flaps is improved. The tip vortices of the wing is stressed due to the ground effect, and moves gradually to the wing tip outboard, therefore, the down-wash flow induced by the tip vortices is weakened. Moreover PIV technique was used to measure the influence of ground effect to the velocity distribution around the Gurney flap as well.