一种新型垂尾抖振抑制方法实验研究

现代高性能三角翼/双垂尾布局战斗机的垂尾结构普遍受到严重的非定常抖振载荷的困扰。根据自诱导理论提出了一种新型的垂尾抖振抑制方法,利用机头处的静态或振动式硬质鼓包,使三角翼前缘涡涡核弯曲、扭转,从而改变前缘涡的轨迹,延缓涡的破裂,减弱前缘涡破裂尾迹在垂尾周围流场处的脉动强度,以达到抑制垂尾抖振的目的。在西北工业大学低湍流度风洞实验室进行了风洞实验,实验所用模型为一个铝制的全机模型,该模型由一个70°大后掠的三角翼,以及两个31°后掠的垂尾组成。风洞内实验段的风速为10m/s 以及20m/s,迎角范围为20°~50°。实验目的是测量机头处的静态或振动式球形鼓包对垂尾抖振的抑制效果。在尾翼根部两侧粘贴有半桥连接的应变片,用以测量尾翼根部的应变,以此应变作为尾翼抖振强度的衡量标准。实验结果表明,不论是静态的还是振动式的鼓包都不同程度地减缓垂尾的抖振响应,振动式鼓包对垂尾的抖振抑制效果与鼓包的振动频率有关。某一侧的鼓包仅对该侧的垂尾抖振有抑制效果,它不影响另一侧垂尾的抖振响应。频谱分析的结果表明,鼓包在抑制垂尾抖振的同时并没有改变垂尾振动的主频。

Experimental study on a novel method for vertical tail buffet suppression

The twin tails of the modern high performance fighter aircrafts with delta wing/twin vertical tails configuration generally experience significant dynamic load due to aerodynamic buffet caused by highly unsteady vortex breakdown flow.This paper proposes a new type of buf-fet alleviation method by solid static or oscillating bulges attached on the forebody of a delta wing model,and conducts wind tunnel experiment for the model which consists of a sharp-edged,70-degree leading edge sweep delta wing,and twin 31°leading edge sweep vertical tails.The model has been tested at 10m/s and 20m/s of free stream velocity,and at angle of attack ranging from 20°to 50°with an interval of 2°in the low-speed wind tunnel at Northwestern Polytechnical Uni-versity.According to the self-induced theory proposed by experts from University of Washing-ton,the bulges attached on the forebody of a delta wing would twist and kink the vortex core, change the vortex trajectory after the bulge,delay the vortex breakdown position,and decrease the fluctuating level of the flow around the twin vertical tails.Thus the goal of buffeting suppres-sion is achieved.This study aims at investigating the buffet alleviation effect of the static or vi-brating bulges attached on the forebody surface of the model.Two pairs of half bridged strain gauges are employed for the measurement of unsteady root strain on the vertical tails,with one pair on each side.The experimental results show that both static and vibrating bulges behave positively as a novel tool to alleviate tail buffet,and the alleviation effect correlates with the vi-brating frequency.Besides,the bulge on one side can only alleviate the buffeting for the tail of the same side,and it has no obvious alleviation effect for the tail on the opposite side.Results of spectral analysis prove that the bulges used in this experiment could alleviate tail buffeting,but they do not change the dominant frequency of the oscillation of the tails in the vortex breakdown flow.