Time-resolved vortex wake of a common swift flying over a range of flight speeds
Time-resolved vortex wake of a common swift flying over a range of flight speeds
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DOI：
10.1098/rsif.2010.0533
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发表时间：
2011-06-06
影响因子：
3.9
通讯作者：
Hedenstrom, A.
中科院分区：
文献类型：
--
作者：
Henningsson, P.;Muijres, F. T.;Hedenstrom, A.
自由飞翔的雨燕（Apus apus L.）在风洞中以5.7、7.7和9.9 m s（-1）三种不同的飞行速度进行了试验。采用高速立体数字粒子图像测速技术（DPIV）对鸟尾流进行了可视化。尾流图像在垂直于气流的横向平面中记录。之前已经使用DPIV并记录平行于气流的纵向平面中的尾流图像来研究雨燕的尾流。高速DPIV系统允许进行时间分辨尾流采样，结果显示了以前研究中没有发现的特征，但大约有40%的垂直力不足。正如早期的研究还显示，一对翼尖涡是尾随在翼尖后面，但此外，一对尾涡和一对“翼根涡”被发现，似乎起源于机翼/机身连接。翼根涡的存在表明，两个机翼并不是作为一个单一的机翼，但在某种程度上是空气动力学相互分离。有人认为这是由于机身产生的升力比机翼小，从而干扰了机翼上的升力分布。
The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s(-1). The wake of the bird is visualized using highspeed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of 'wing root vortices' are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings.