Abstract This work aims to control the unsteady flow structure of a NACA0012 under full stall by limiting the vortex roll-up from its trailing edge. In this regard, plates with varying lengths at zero incidences were attached at the trailing edge of the airfoil at an angle of attack of α = 16o and low Reynolds number of Rec = 2.0×104. Under these conditions, the flow separates near the leading edge and rolls up (without reattachment) into the wake with a subsequent supercritical mode vortex shedding corresponding to the full stall condition. Planar PIV measurements were performed in a closed-loop water channel to analyze the effect of plate length on the wake characteristics of the airfoil. Turbulent flow structures of baseline airfoil and airfoil with various plate lengths (l /c = 0.1, 0.2, 0.3) were revealed and elaborated with time-averaged turbulent statistics, two-point correlations, spectral analysis, and instantaneous vorticity contours. According to the results, vortex roll-up from the trailing edge and corresponding turbulent structures were partially suppressed by the use of plates with l /c = 0.2 and l /c =0.3 by elongating the vortex formation length. Besides, two-point correlations of fluctuating velocity components revealed that the use of trailing edge plates of l /c > 0.1 is effective in decreasing the size and magnitude of turbulent structures. Consequently, the turbulent fluctuations were found to be reduced, and the vortex shedding frequency was attenuated in the near wake of the airfoil.

中文翻译：

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使用固定后缘板控制完全失速时机翼附近的气流

摘要 这项工作旨在通过限制从其后缘卷起的涡旋来控制全失速下 NACA0012 的非定常流动结构。在这方面，具有不同长度的零入射角的板以 α = 16o 的攻角和 Rec = 2.0×104 的低雷诺数连接在翼型的后缘。在这些条件下，流动在前缘附近分离并卷起（没有重新附着）进入尾流，随后出现对应于完全失速条件的超临界模式涡旋脱落。在闭环水道中进行平面 PIV 测量，以分析板长度对翼型尾流特性的影响。基线翼型和不同板长（l / c = 0.1, 0.2, 0. 3) 用时间平均湍流统计、两点相关性、谱分析和瞬时涡度等值线揭示和阐述。根据结果​​，通过延长涡流形成长度，使用 l /c = 0.2 和 l /c = 0.3 的板，部分抑制了来自后缘的涡旋卷起和相应的湍流结构。此外，波动速度分量的两点相关性表明，使用 l / c > 0.1 的后缘板可有效降低湍流结构的大小和幅度。因此，发现湍流波动减少，涡旋脱落频率在翼型尾流附近衰减。通过使用l / c = 0.2和l / c = 0.3的板，通过延长涡旋形成长度，部分抑制了从后缘卷起的涡旋和相应的湍流结构。此外，波动速度分量的两点相关性表明，使用 l / c > 0.1 的后缘板可有效降低湍流结构的大小和幅度。因此，发现湍流波动减少，涡旋脱落频率在翼型尾流附近衰减。通过使用l / c = 0.2和l / c = 0.3的板，通过延长涡旋形成长度，部分抑制了从后缘卷起的涡旋和相应的湍流结构。此外，波动速度分量的两点相关性表明，使用 l / c > 0.1 的后缘板可有效降低湍流结构的大小和幅度。因此，发现湍流波动减少，涡旋脱落频率在翼型尾流附近衰减。波动速度分量的两点相关性表明，使用 l / c > 0.1 的后缘板可有效降低湍流结构的大小和幅度。因此，发现湍流波动减少，涡旋脱落频率在翼型尾流附近衰减。波动速度分量的两点相关性表明，使用 l / c > 0.1 的后缘板可有效降低湍流结构的大小和幅度。因此，发现湍流波动减少，涡旋脱落频率在翼型尾流附近衰减。