Vortex formation around an oscillating and translating airfoil at large incidences
Vortex formation around an oscillating and translating airfoil at large incidences
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DOI：
10.1017/s0022112090001483
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发表时间：
1990-02
影响因子：
3.7
通讯作者：
K. Ohmi;M. Coutanceau;T. Loc;A. Dulieu
中科院分区：
文献类型：
--
作者：
K. Ohmi;M. Coutanceau;T. Loc;A. Dulieu
通过可视化实验和数值计算，研究了二维振荡平动翼型的起动流动。翼型，椭圆形的横截面，设置在运动的冲动，并同时受到一个稳定的翻译和谐波振荡的俯仰。翼型的冲角在0°和45°之间变化，基于弦长的雷诺数在1500和10000之间。本研究的主要目的是揭示振荡翼型在超过静态失速角的大迎角下产生的非定常涡的一些显著特征。另一个目的是详细地研究主要实验参数对涡尾发展的各自和综合影响。结果表明，在一般情况下，流动的主导参数是降低频率不仅当翼型振荡在接近静态失速角的入射角，但也在较大的入射角。研究还表明，随着俯仰频率的增加，涡尾流的图案取决于约化频率和振幅的乘积，而不是取决于频率本身。指出高的折合频率和大的振幅的组合效应可引起前缘涡的循环叠加，由此在上表面上发展出逐渐扩展的驻涡。
The starting flows past a two-dimensional oscillating and translating airfoil are investigated by visualization experiments and numerical calculations. The airfoil, elliptic in cross-section, is set in motion impulsively and subjected simultaneously to a steady translation and a harmonic oscillation in pitch. The incidence of the airfoil is variable between 0° and 45° and the Reynolds number based on the chord length is between 1500 and 10000. The main object of the present study is to reveal some marked characteristics of the unsteady vortices produced from the oscillating airfoil set at large incidences in excess of the static stall angle. Another purpose is to examine, in some detail, the respective and combined effects of the major experimental parameters on the vortex wake development. It is shown that, in general, the dominant parameter of the flow is the reduced frequency not only when the airfoil oscillates at incidences close to the static stall angle but also at larger incidences. It is also demonstrated that, as the pitching frequency is increased, the patterns of the vortex wake are dependent on the product of the reduced frequency and the amplitude rather than on the frequency itself. It is noted that the combined effect of a high reduced frequency and a large amplitude can give rise to cyclic superposition of leading-edge vortices from which a gradually expanding standing vortex is developed on the upper surface.