实验测量了超低雷诺数(Re=5 300)下NACA 0012翼型在自由来流下的升力系数和阻力系数,重点研究来流的湍流度对升力系数和阻力系数的影响,并进一步通过对翼型流场的研究揭示湍流度对翼型受力产生影响的机理。结果显示,低湍流度下升力系数和阻力系数均无失速特征;当湍流度提高,升力系数和阻力系数在12°~15°迎角下表现出明显的失速特征。翼型流场的流动显示表明,自由来流的湍流度不仅对翼型边界层的流动有明显影响,而且对边界层分离后的剪切层流动状态有很大影响,使得翼型在相同雷诺数和相同迎角下表现出完全不同的特性,并得出湍流度的增大和雷诺数的提高在影响翼型绕流形态及受力特征方面起着相似作用的结论。

The present study measures the lift and drag coefficients of airfoil NACA 0012 at ultra-low Reynolds number (Re=5 300) in an experiment. The investigation focuses on the free-stream turbulence intensity effect on airfoil lift coefficient and dray coefficient, and further explains this effect through a discussion of turbulence intensity influence on airfoil flow. The measured results indicate that, while airfoil stall does not occur in lift coefficient and drag coefficient for low turbulence intensity, it is clearly present for high turbulence intensity. For airfoil NACA 0012 and high turbulence intensity, the stall occurs at angles of attack from 12° to 15°. As demonstrated by the flow visualization around the airfoil, the influence of turbulence intensity is significant on both the airfoil boundary layer and the separated shear layer, so that the airfoil performance differs at different turbulence intensity. In addition, the influence of the increase of turbulence intensity and Re appears to be similar on the airfoil load characteristic and flow regime.