On the distribution of leading-edge vortex circulation in samara-like flight
On the distribution of leading-edge vortex circulation in samara-like flight
复制标题
DOI：
10.1017/jfm.2015.279
复制
发表时间：
2015-08-01
影响因子：
3.7
通讯作者：
Rival, David E.
中科院分区：
文献类型：
--
作者：
Limacher, Eric;Rival, David E.
作为自然萨马拉飞行的一种抽象形式，本文研究了自由流中稳定旋转的平板。在翼展法向平面上进行的粒子图像测速表明，增加旋转，如无量纲参数的叶尖速度比所捕获的，会导致从海崖体到稳定的前缘涡的平均尾流拓扑结构的过渡。尽管叶尖速比的变化对拓扑结构有显著影响，但在给定的展向位置、局部有效攻角和局部有效速度下，叶尖速比的变化对前缘环量的影响可以忽略不计。通过比较不同扭转剖面的旋转板，在不同的叶尖速比下有效攻角分布保持不变。在前缘的剪切层速度分布也被解决，允许通过前缘剪切层的涡通量的量化。有趣的是，观测到的环流平衡值对切变层涡度通量的变化并不敏感。
As an abstraction of natural samara flight, steadily rotating plates in a free-stream flow have been studied. Particle image velocimetry on span-normal planes has been conducted to show that increasing rotation, as captured by the dimensionless parameter of tip speed ratio, causes a transition of the mean wake topology from that of a bluff body to that of a stable leading-edge vortex. Despite its notable effect on topology, a change in tip speed ratio has negligible effect on leading-edge circulation at a given spanwise position, local effective angle of attack and local effective velocity. The effective angle-of-attack distribution was held constant at different tip speed ratios by comparing rotating plates with different twist profiles. The shear-layer velocity profile at the leading edge was also resolved, allowing quantification of the vorticity flux passing through the leading-edge shear layer. Interestingly, the observed equilibrium values of circulation are not sensitive to changes in shear-layer vorticity flux.