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首页> 外文期刊>Journal of the American Helicopter Society >Collaborative Investigation of the Aerodynamic Behavior of Airfoils in Reverse Flow
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Collaborative Investigation of the Aerodynamic Behavior of Airfoils in Reverse Flow

机译：逆流机翼气动行为的协同研究。

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Two (static and dynamic) fundamental models of the flow over airfoils in the reverse flow region of a helicopter in forward flight are investigated experimentally and computationally at Reynolds numbers of O(10(5)). The first model examines the time-averaged and unsteady flow resulting from a two-dimensional NACA 0012 airfoil held at a static angle of attack. Computational tools successfully predict the presence of three unsteady wake regimes and time-averaged airloads measured experimentally at the University of Maryland (UMD). A second model is investigated by pitching a two-dimensional NACA 0012 airfoil through deep dynamic stall in reverse flow. Both experimental and computational results reveal flow separation at the sharp leading edge for shallow angles of attack, leading to the early formation of a reverse flow dynamic stall vortex. Subsequent flow features in the pitching cycle (i.e., a trailing edge vortex and a secondary dynamic stall vortex) are also captured by the numerical simulation, although the timing and strength of some of these features do not align completely with experiment. This work gives fundamental insight into the aerodynamic behavior of airfoils in reverse flow, improves understanding of the complex nature of the reverse flow region, and demonstrates a promising new computational tool for simulating this unique flow regime.
机译：在O（10（5））的雷诺数下，通过实验和计算研究了直升飞机反向流动区域中机翼上的流动的两个（静态和动态）基本模型。第一个模型检查了二维NACA 0012机翼保持在静态迎角时产生的时间平均和非恒定流。计算工具成功地预测了在马里兰大学（UMD）进行实验测得的三种非稳态唤醒方式和时均空载的存在。通过反向流动中的深动态失速使二维NACA 0012翼型俯仰来研究第二种模型。实验和计算结果均表明，在较浅的迎角下，尖锐前缘处的流动分离，从而导致逆流动态失速旋涡的早期形成。尽管这些功能中某些功能的时间和强度与实验并不完全吻合，但俯仰周期中的后续流动特征（即后缘涡流和次级动态失速涡流）也可以通过数值模拟来捕获。这项工作对机翼在逆流中的空气动力学行为提供了基本的见识，增进了对逆流区域的复杂性质的理解，并展示了一种有前途的新型计算工具，可以模拟这种独特的流态。

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