A Computational Study of a Canonical Pitch-Up, Pitch-Down Wing Maneuver
A Computational Study of a Canonical Pitch-Up, Pitch-Down Wing Maneuver
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DOI：
10.2514/6.2009-3687
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发表时间：
2009-06
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影响因子：
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通讯作者：
J. Eldredge;Chengjie Wang;M. Ol
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文献类型：
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作者：
J. Eldredge;Chengjie Wang;M. Ol
通过对Navier-Stokes方程的直接数值模拟，研究了在均匀流动中进行单次线性俯仰/俯仰下机动的二维翼型的简单正则问题。研究了螺距率和雷诺数对椭圆型和薄型平板的影响。特别地，计算了雷诺数为10 2 - 10 4时的流动，并对由此产生的升力、阻力和涡脱落进行了研究。研究发现，在俯仰上升过程中，所有力都随俯仰率的增加而单调增加，并且在俯仰下降的大部分时间内，大的俯仰率会产生净推力和负升力。随着雷诺数的增加，俯仰升力明显增大。平板机翼通常比椭圆机翼产生更大的升力，但代价是阻力更大。在低螺距速率下，在俯仰上升过程中形成较大的前缘涡，在俯仰下降过程中脱落，尾迹涡较弱且相对扩散。相反，高螺距率会导致更强、更紧凑的前缘和尾流涡。尾流涡表现出明显的配对，前缘涡表现出较小的分离倾向。将力的产生与脱落观测联系起来的表面压力分布证实了前缘涡在升力产生中的重要作用。在俯仰下降过程中，在低俯仰速率下，前缘涡的升力克服下压力产生正升力，而在高俯仰速率下，下压力占主导地位。雷诺数为104时的涡度场与OL （AIAA Paper 2009-3686）在配套实验研究中的相应结果比较好。
The simple canonical problem of a two-dimensional wing profile undergoing a single linear pitch-up/pitch-down maneuver in a uniform flow is studied computationally with direct numerical simulation of the Navier–Stokes equations. The effects of pitch rate and Reynolds number are both studied, for both elliptical and thin flat-plate profiles. In particular, flows at Reynolds numbers of 10 2 – 10 4 are computed, and the resulting lift, drag and vortex shedding are examined. It is found that, during the pitch-up, all forces increase monotonically with increasing pitch rate, and that large pitch rates produce a net thrust and negative lift during most of the pitch-down interval. The pitch-up lift is notably larger as Reynolds number increases. A flat plate generally produces greater lift than an elliptical wing, at the cost of greater drag. At low pitch rates, a large leading-edge vortex is formed during the pitch-up and is shed during the pitch-down, and wake vortices are weak and relatively diffuse. In contrast, high pitch rates lead to stronger, more compact leading-edge and wake vortices. The wake vortices exhibit distinct pairing, and the leading-edge vortex shows less tendency to separate. Surface pressure distributions, which are used to connect the force generation with these shedding observations, confirm the important role of the leading-edge vortex in lift generation. During pitch-down, at low pitch rates the lift from the leading-edge vortex overcomes the downforce to produce positive lift, whereas downforce dominates at high pitch rates. Vorticity fields at Reynolds number 10 4 compare very well with corresponding results of OL (AIAA Paper 2009-3686) in the companion experimental study.