The effect of advance ratio on the aerodynamics of revolving wings
The effect of advance ratio on the aerodynamics of revolving wings
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DOI：
10.1242/jeb.01266
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发表时间：
2004-11-01
影响因子：
2.8
通讯作者：
Dickinson, MH
中科院分区：
文献类型：
--
作者：
Dickson, WB;Dickinson, MH
最近的研究表明，一个准定常模型密切匹配的瞬时力产生的昆虫翅膀在悬停飞行。然而，尚不清楚这种方法是否适用于向前飞行。在这项研究中，我们使用一个动态缩放的机器人模型的果蝇黑腹果蝇调查所产生的力量由一个翅膀旋转在恒定的角速度，同时翻译速度适合向前飞行。由于前进速度和角速度恒定，机翼惯性可以忽略不计，并且测量的力可以归因于流体动力学现象。机翼的前向和旋转运动产生了一个随时间变化的自由流速度剖面，这表明附加的质量力对测得的力有贡献。我们发现，由于增加质量的力量，使一个小的，但可测量的，总的力量的组成部分，并与理论值非常吻合。升力和阻力系数是从力迹线减去附加质量的贡献后计算出来的。对于固定迎角，升阻系数在非零提前比时不是常数，而是在整个冲程中变化。这一观察结果意味着，为了准确地预测前飞过程中产生的瞬时力，需要对准定常模型进行修正。我们表明，升力系数和阻力系数对前进比和冲程位置的依赖性可以有效地用翼尖速度比来表征，翼尖速度比是由于平移和旋转引起的翼尖处气流速度的弦向分量之比。在此基础上，我们开发了一个修改后的准定常模型，可以考虑到不同幅度的升力和阻力系数。我们的模型也可以解决以往基于平移和旋转运动的机翼性能测量的差异。
Recent studies have demonstrated that a quasi-steady model closely matches the instantaneous force produced by an insect wing during hovering flight. It is not clear, however, if such methods extend to forward flight. In this study we use a dynamically scaled robotic model of the fruit fly Drosophila melanogaster to investigate the forces produced by a wing revolving at constant angular velocity while simultaneously translating at velocities appropriate for forward flight. Because the forward and angular velocities were constant wing inertia was negligible, and the measured forces can be attributed to fluid dynamic phenomena. The combined forward and revolving motions of the wing produce a time-dependent free-stream velocity profile, which suggests that added mass forces make a contribution to the measured forces. We find that the forces due added mass make a small, but measurable, component of the total force and are in excellent agreement with theoretical values. Lift and drag coefficients are calculated from the force traces after subtracting the contributions due to added mass. The lift and drag coefficients, for fixed angle of attack, are not constant for non-zero advance ratios, but rather vary in magnitude throughout the stroke. This observation implies that modifications of the quasi-steady model are required in order to predict accurately the instantaneous forces produced during forward flight. We show that the dependence of the lift and drag coefficients upon advance ratio and stroke position can be characterized effectively in terms of the tip velocity ratio - the ratio of the chordwise components of flow velocity at the wing tip due to translation and revolution. On this basis we develop a modified quasi-steady model that can account for the varying magnitudes of the lift and drag coefficients. Our model may also resolve discrepancies in past measurements of wing performance based on translational and revolving motion.