Investigation of laminar separation bubble over a supercritical airfoil in an incompressible flow
Investigation of laminar separation bubble over a supercritical airfoil in an incompressible flow
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不可压缩流动中超临界翼型层流分离气泡的研究
DOI：
10.1177/09544062211020773
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
Massoud Tatar;M. Masdari;M. Tahani
中科院分区：
文献类型：
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作者：
Massoud Tatar;M. Masdari;M. Tahani
超临界翼型在不可压缩流态下具有未知的特性，其跨音速雷诺数低于其设计点。在这项工作中，边界层转捩研究了超临界翼型的热膜和压力的测量与数值模拟完成。实验在弦基雷诺数为8.11 × 105，马赫数为0.1的条件下进行，并在不同攻角下进行。对超临界翼型上表面的热膜进行了测量，并利用信号的标准差计算了转捩点。还记录了上表面压力，并将其二阶导数中的峰值作为层流分离气泡机制产生的过渡点。此外，一个适当的时频分析应用到热膜信号，以了解过渡边界层结构的频谱内容和发展。另一方面，采用了两种数值程序，并将数值模拟获得的转变点与实验结果进行了比较。结果表明，当迎角增加到2 °时，上表面气泡位置迅速变化。层流分离泡在表面压力分布数据中被观察到，并且利用其沿流向方向的二阶导数沿着被很好地识别。通过时频分析，对层流边界层的频谱特性进行了研究，包括层流边界层的流向波动、过渡区的间歇性以及湍流边界层的宽频谱范围。一个有前途的协议之间的过渡点计算的数值和实验研究，并确认了二阶导数的表面压力数据，热膜测量和可靠性的数值过渡模型优化研究所取得的结果的准确性。
Supercritical airfoils have an unknown behavior at incompressible flow regime and Reynolds numbers lower than those related to their design point at transonic condition. In this work, boundary layer transition is studied over a supercritical airfoil by means of hot-film and pressure measurements completed with numerical simulations. The experiments are performed at chord-based Reynolds number of 8.11 × 10 5 and Mach number of 0.1 at different angles of attack. Hot-film measurement over the upper surface of the supercritical airfoil is carried out and the transition points are computed using the standard deviation of the signals. The upper surface pressure is also recorded and a peak in its second derivative is presented as the transition point generated by the laminar separation bubble mechanism. Moreover, an appropriate time-frequency analysis is applied to the hot-film signals to get an insight into the spectral content and development of the transitional boundary layer structures. On the other hand, two numerical codes are employed and the transition points obtained from numerical simulations are compared with the experimental outcomes. Results express a rapid change of the bubble position over the upper surface, as the angle of attack is increased to the value of 2 ° . Laminar separation bubble is observed in the surface pressure distribution data and is well identified using its second derivative along the streamwise direction. The spectral characteristics of the boundary layer are satisfactorily explored including the streamwise fluctuations within the laminar flow, intermittent behavior of the transitional zone and the wide range of the spectrum in turbulent flow, thanks to the time-frequency analysis. A promising agreement is observed between the transition points computed by both the numerical and experimental studies and confirms the accuracy of findings achieved by the second derivative of surface pressure data, hot-film measurements and the reliability of the employed numerical transition models for optimization studies.