Separation-Bubble-Transition Measurements on a Low-Re Airfoil Using Particle Image Velocimetry
Separation-Bubble-Transition Measurements on a Low-Re Airfoil Using Particle Image Velocimetry
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DOI：
10.1115/gt2005-68663
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
B. McAuliffe;M. Yaras
中科院分区：
文献类型：
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作者：
B. McAuliffe;M. Yaras
本文介绍了用粒子图像测速仪(PIV)在翼型上测量低雷诺数和低自由流湍流条件下分离-气泡转变的实验结果。在一个水箱装置中，对低雷诺数翼型的吸力面进行了二维PIV测量。基于翼型弦长和拖曳速度的雷诺数在不同的入射角度下分别为40,000和65,000，提供了一系列沿流方向的压力分布和过渡的分离气泡几何形状。观察到的气泡类型从靠近翼型前缘分离的短而厚的气泡，到远离吸力峰下游的分离的长而细的气泡。PIV测量有助于显示与分离-气泡转变相关的旋涡动力学。通过瞬时矢量场记录了不稳定波在分离的剪切层中的增长和最终分解为湍流的过程。在所考察的所有情况下，在再附着区观察到了大范围的旋涡脱落和多个逆流区。提出了一种基于统计湍流量来估计转移点位置的技术，并与现有的转移点模型进行了比较
This paper presents experimental results on separation-bubble transition at low Reynolds number and low freestream turbulence, measured on an airfoil using particle image velocimetry (PIV). The two-dimensional PIV measurements have been performed over the suction surface of a low-Reynolds-number airfoil in a water tow-tank facility. Reynolds numbers, based on airfoil chord length and towing speed, of 40,000 and 65,000 have been examined at various angles of incidence, providing a range of streamwise pressure distributions and transitional separation-bubble geometries. The types of bubbles observed range from a short and thick bubble with separation near the leading edge of the airfoil, to a long and thin bubble with separation far downstream of the suction peak. The PIV measurements facilitate visualization of the vortex dynamics associated with separation-bubble transition. The growth of instability waves within the separated shear layer and eventual breakdown into turbulence is documented through the instantaneous vector fields. For all cases examined, large-scale vortex shedding and multiple reverse-flow zones are observed in the reattachment region. A technique for estimating the location of transition onset based on statistical turbulence quantities is presented, and comparisons are made to existing transition models.Copyright © 2005 by ASME