A criterion for vortex separation on unsteady aerodynamic profiles
A criterion for vortex separation on unsteady aerodynamic profiles
复制标题
非定常气动轮廓上涡分离的判据
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
C. Tropea
中科院分区：
文献类型：
--
作者：
D. Rival;J. Kriegseis;P. Schaub;Alexander Widmann;C. Tropea
已经进行了自由表面水隧道中前缘涡 (LEV) 增长和脱离的实验，其中包括直接力和粒子图像测速测量。测试在雷诺数 Re = 10 下进行； 000，减少的频率 k = 0:25 和 Strouhal 数 St = 0:16，后两者是自然界中在大范围雷诺数上的典型的游泳和游泳。显示前缘形状影响进料剪切层；因此开发了LEV。对于 LEV 增长的延迟开始，剖面表面上的涡量喷发过程也可以延迟，从而推迟供给层和喷发层的交叉湮灭。这种效应反过来又延迟了后缘 (LEV) 驻点的到达，一旦突破，就会导致半鞍升起并形成全鞍，进而允许后缘涡量向前快速馈送以切断 LEV。因此，后缘（弦长）在限制 LEV 大小（循环）方面起着关键作用，因此被发现是雷诺数较高时涡旋分离过程最具特征的长度尺度，其中喷发过程将不太明显。
Experiments on leading-edge vortex (LEV) growth and detachment in a free-surface water tunnel with ve plunging leading-edge pro les have been conducted, comprising direct-force and Particle Image Velocimetry measurements. The tests have been performed at a Reynolds number of Re = 10; 000, a reduced frequency of k = 0:25 and a Strouhal number of St = 0:16, the latter two being typical of ying and swimming in nature over a large range of Reynolds numbers. The leading-edge shape is shown to in uence the feeding shear layer; hence the development of the LEV. For a delayed onset of LEV growth, the vorticity-eruption process on the pro le surface can also be delayed, such that the crossannihilation of the feeding and eruption layers is postponed. This e ect in turn delays the arrival of the rear (LEV) stagnation point at the trailing edge, which, once breached, causes the half saddle to lift o and form a full saddle, in turn allowing the rapid feeding of trailing-edge vorticity forward to cut o the LEV. Therefore, the trailing edge (chord length) plays a critical role of limiting the LEV size (circulation) and as such is found to be the most characteristic length scale for the vortex-separation process at higher Reynolds numbers, where the eruption process will be less pronounced.