Abstract To gain insight on how freestream turbulence (FST) affects the aerodynamics of an airfoil in a systematic manner, the present study investigates a NREL S826 airfoil subjected to seven different incoming flows with varying degrees of FST. The Reynolds number was held at Rec ​= ​4.0 ​× ​105, while the turbulence intensity (Ti) was varied between 0.4% and 5.4%. An increase in Ti increases the maximum lift while having negligible effects on the stall angle. The lift slope in the linear region also generally increased with higher Ti. The latter observation contrasts with some earlier studies, and incoming flow homogeneity is a potential contributing factor to the differences seen here. Periodic pressure fluctuations are seen in the computed lift time-series signal when Ti is between 1% and 2% and the airfoil is operating in the linear region. These fluctuations arise from surface pressure oscillations that are likely excited by the relatively low incoming Ti. The overall effect is a reduction in the time-averaged lift under these operating conditions. At higher Ti, more energetic boundary layers develop over the airfoil’s suction side and the effect of these periodic pressure fluctuations is suppressed, leading to an increase in the produced lift.

中文翻译：

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自由流湍流对翼型时间压力分布和升力的影响

摘要 为了深入了解自由流湍流 (FST) 如何以系统的方式影响翼型的空气动力学，本研究调查了 NREL S826 翼型，该翼型受到 7 种不同程度 FST 的不同来流影响。雷诺数保持在 Rec = 4.0 × 105，而湍流强度 (Ti) 在 0.4% 和 5.4% 之间变化。Ti 的增加会增加最大升力，同时对失速角的影响可以忽略不计。线性区域的升力斜率也普遍随着 Ti 的升高而增加。后一种观察与一些早期的研究形成对比，流入的流动均匀性是造成此处所见差异的潜在因素。当 Ti 介于 1% 和 2% 之间并且翼型在线性区域中运行时，在计算的升力时间序列信号中可以看到周期性压力波动。这些波动是由相对较低的输入 Ti 可能激发的表面压力振荡引起的。总体效果是在这些操作条件下降低了时间平均升力。在较高的 Ti 下，机翼吸力侧上会形成更多能量边界层，并且这些周期性压力波动的影响被抑制，导致产生的升力增加。