基于涡系相交不稳定性的飞机尾流控制方法

在飞机飞行的过程中尾涡会伴随着升力产生,威胁后机的飞行安全.在简化机翼模型上添加扰流片,通过一个矩形翼以引入一个与主翼尾涡大小不同、方向相反的小涡,构建尾流自消散四涡系统,以期诱发尾涡的Rayleigh-Ludwig相交不稳定性.通过改变扰流片的大小形状,调整模型的攻角和拖曳速度,采用粒子图像速度场仪测量系统定量研究在低雷诺数下单主翼尾涡发展特性以及双涡相互作用特性.研究表明:在未添加扰流片时,尾涡环量在45个翼展内相对于初始环量基本保持不变;在添加扰流片的情况下尾涡的环量衰减可以达到35%~55%,而未添加的基本翼型的尾涡的环量则几乎保持不变,这说明添加适当的扰流片能诱发尾涡的Rayleigh-Ludwig相交不稳定性,加速尾涡的消散,当小涡和主涡的初始环量比为-0.489、初始距离比为0.5时,45个翼展范围内,尾涡环量衰减55.9%.本文系统性的实验结果可以为低尾流机翼的设计提供参考依据. 

Control method for aircraft wake vortex based on Rayleigh-Ludwig instability

The aircraft wake vortex is an inherent flow phenomenon due to the lift generation mechanism, which has a negative impact on the flight safety. By adding a set of specially designed spoiler, a rectangular wing was designed to generate a pair of weaker vortices, which had different sizes and opposite direction compared to main wing vortices, thereby constructing a self-destructive four-vortex wake system to induce Rayleigh-Ludwig instability. Under different experimental conditions, in terms of changing the size or shape of the spoiler, towing speed and angle of attack, the wake vortex development of the test model, that both with and without spoiler, as well as the circulation analysis, were acquired particle image velocimetry (PIV) measurements under the low Reynolds number. The study demonstrates that the decrease in circulation was 35% to 55% in 45 wingspans when spoilers are introduced, whereas the counterpart of the baseline airfoil, without spoilers, is nearly kept steadily, which reveal the application possibility of Rayleigh-Ludwig instability in alleviating the wake vortex. As the initial circulation ratio equals to -0.489 and the initial distance ratio is 0.5, the circulation of the primary vortex reduce most significantly (55.9%) in 45 wingspans. Results would provide a scheme in the design of airfoils with weaker vortices.