Large Eddy simulation of a heaving wing on the Cusp of transition to turbulence
Large Eddy simulation of a heaving wing on the Cusp of transition to turbulence
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DOI：
10.1016/j.compfluid.2019.03.023
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发表时间：
2019-04
影响因子：
2.8
通讯作者：
C. Badoe;Zheng-Tong Xie;N. Sandham
中科院分区：
文献类型：
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作者：
C. Badoe;Zheng-Tong Xie;N. Sandham
为了研究NACA 0012机翼失速前后的分离流动现象，对NACA 0012升沉机翼的绕流进行了数值模拟。采用广泛应用的高保真大涡模拟(LES)方法，研究了雷诺数Rec=2 × 104时基于弦线的非定常气动载荷和流动结构。当弦线归一化峰-峰振幅OFA/c=0.5时，攻角分别为5∘和15∘时，K=0.47和0.94的折合频率分别代表失速前和失速后状态。与实验结果的比较表明，相平均升力、阻力和力矩与实验结果吻合较好。分析了动态失速的特征现象，重点分析了前缘涡的发展。一系列瞬时展向涡度图显示，在下击开始时，在吸力面上发展的逆流区存在显著的展向扰动，导致分离的剪切层不稳定。这种不稳定性导致了前缘机翼表面附近首次出现湍流。
Simulations of the flow over a heaving NACA 0012 wing are conducted to study the separated flow phenomena for a pre-stall and post-stall wing condition. An extensively validated high fidelity large-eddy simulation (LES) approach is used to examine the unsteady aerodynamic loads and flow structures at Reynolds numberRec= 2 × 104based on the chord. We consider reduced frequencies ofk= 0.47 and 0.94 for a chord-normalized peak-to-peak amplitude ofA/c=0.5 and angles of attack of 5∘and 15∘, representing pre-stall and post-stall conditions respectively. Comparison to experiment shows good agreement for the phase-averaged lift, drag and moments of the heaving wing. Characteristic phenomena of dynamic stall are analysed with emphasis on the leading edge vortex (LEV) development. A series of instantaneous spanwise vorticity plots show significant spanwise perturbations in the reverse flow region that develops over the suction surface during the start of the downstroke, giving rise to instabilities in the detached shear layer. The instabilities give rise to the first occurrence of turbulence near the wing surface at the leading edge.