The onset of dynamic stall at a high, transitional Reynolds number
The onset of dynamic stall at a high, transitional Reynolds number
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DOI：
10.1017/jfm.2018.939
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发表时间：
2019-02-25
影响因子：
3.7
通讯作者：
Visbal, M. R.
中科院分区：
文献类型：
--
作者：
Benton, S. I.;Visbal, M. R.
采用壁面分辨大涡模拟方法，研究了雷诺数Re_c = 1.0 × 10 ~（6）时NACA 0012翼型斜坡式俯仰运动引起的动态失速。重点放在机翼接近失速时发展的非定常边界层相互作用上。在此雷诺数下，湍流分离向上游移动，穿过大部分翼型吸力面。当湍流分离到达前缘分离泡时，破裂事件开始，导致强相干的前缘涡结构。该涡包裹湍流剪切层，形成大的动态失速涡。大涡模拟的使用阐明了确定动态失速过程开始时层流分离泡的滚动。在Re-c = 0.2 x 10（6）和0.5 x 10（6）的较低雷诺数下，与相同的模拟进行比较。这种比较表明了边界层力学的趋势，解释了动态失速过程对雷诺数的敏感性。
Dynamic stall due to a ramp-type pitching motion is investigated on the NACA 0012 airfoil at chord Reynolds number of Re-c = 1.0 x 10(6) through the use of wall-resolved large-eddy simulation. Emphasis is placed on the unsteady boundary-layer interactions that develop as the airfoil approaches stall. At this Reynolds number it is shown that turbulent separation moves upstream across much of the airfoil suction surface. When turbulent separation reaches the leading-edge separation bubble, a bursting event is initiated leading to a strong coherent leading-edge vortex structure. This vortex wraps up the turbulent shear layer to form a large dynamic stall vortex. The use of large-eddy simulation elucidates the roll of the laminar separation bubble in defining the onset of the dynamic stall process. Comparisons are made to identical simulations at lower Reynolds numbers of Re-c = 0.2 x 10(6) and 0.5 x 10(6). This comparison demonstrates trends in the boundary-layer mechanics that explain the sensitivity of the dynamic stall process to Reynolds number.