Modification of a wing tip vortex by vortex generators
Modification of a wing tip vortex by vortex generators
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DOI：
10.1016/j.ast.2005.04.003
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发表时间：
2005-09
影响因子：
5.6
通讯作者：
A. Heyes;David R. Smith
中科院分区：
文献类型：
--
作者：
A. Heyes;David R. Smith
与运输机有关的涡流尾流危害是众所周知的。一种缓解方法是改变近场尾流拓扑结构，使环流分布在更大的面积上，并减小遇到尾流的后续飞机的滚转力矩。本文描述了使用辅助涡流发生器来改变半翼展翼型的叶尖涡脱落的实验研究结果。实验是在小型低速风洞中进行的，雷诺数为2.2× 105，用粒子图像测速仪测量了瞬时和平均横流流场。结果表明，当涡流发生器配置成产生相对于翼尖涡流同向旋转的涡流时，两者在后缘的五个弦长内合并，导致涡流的尺寸相对于基线尾流的尺寸增大。对各种涡流发生器几何形状进行了测试。半圆形发生器使核心半径增加了五倍，但最好的形状被认为是三角形，因为这种形状的发生器产生了相当大的涡流扩大，升力损失相对较低。低细长比发生器也被认为是优选的，因为对于高细长比发生器，已经表明，由于发生器涡流靠近机翼表面，在翼尖和发生器涡流之间的区域存在负涡量缓冲区，因此合并失败。结果表明，增大发生器攻角可提高环量再分布的有效性。在最大迎角时，尽管由于失速而使VG涡强度减小，但仍出现了增加。失速VG流中的不稳定性似乎增强了涡度扩散，据推测，它也可能引发多个涡系中的合作不稳定性。
The vortex wake hazard associated with transport aircraft is well known. One strategy for its alleviation is to alter the near field wake topology to distribute circulation over an increased area and reduce the consequent rolling moment on a following aircraft encountering the wake. The paper describes the results of an experimental investigation of the use of supplementary vortex generators to modify the tip vortex shed from a half-span airfoil. The experiments were conducted in a small low speed wind tunnel at a chord Reynolds number of 2.2×105and the flow was characterised by measurement of the instantaneous and mean cross-stream flow field using particle image velocimetry. The results show that when the vortex generator is configured to produce a vortex that is co-rotating with respect to the wing-tip vortex, the two merge within five chord-lengths of the trailing edge resulting in a vortex with increased size relative to that of the baseline wake. Various vortex generator geometries were tested. A semi-circular generator produced an increase in core radius by a factor of five but the best shape was deemed triangular since generators of this shape produced substantial vortex enlargement with relatively low lift penalty. Low slenderness ratio generators were also deemed preferable since for a high slenderness generator it was shown that merging failed due to a negative vorticity buffer constrained to the region between the tip and generator vortex by the proximity of the generator vortex to the wing surface. Increasing the generator angle of attack was shown to increase the effectiveness of circulation redistribution. At the highest angles of attack increases occurred despite a decrease in VG vortex strength due to stalling. Unsteadiness in the stalled VG flow appears to enhance vorticity diffusion and it is hypothesised that it may also initiate cooperative instabilities in multiple vortex systems.