On the quasi-steady aerodynamics of normal hovering flight part I: the induced power factor
On the quasi-steady aerodynamics of normal hovering flight part I: the induced power factor
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DOI：
10.1098/rsif.2013.1196
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发表时间：
2014-04-06
影响因子：
3.9
通讯作者：
Crowther, William J.
中科院分区：
文献类型：
--
作者：
Nabawy, Mostafa R. A.;Crowther, William J.
对于正常悬停状态下的扑翼，给出了一种量化诱导功率因数k中捕获的损失的分析处理，包括非均匀下洗、尖端损失和有限扑翼振幅的影响。该方法基于一种新颖的驱动盘和提升线叶片理论的结合，并考虑了超前比的影响。根据文献的实验结果对模型进行了评价，并对推进比对旋转翼升力系数的影响进行了定性分析。与果蝇翼展的环流定量实验数据对比表明，该模型能够正确预测环流形状的变化，包括峰值环流的大小和环流向零衰减的速率。对八种昆虫正常悬停时诱导功率因子的贡献进行了评价。本文还说明了如何在诱导功率因数中考虑雷诺数，并且在预测的跨度效率作为雷诺数的函数与文献中的数值结果之间取得了很好的一致性。最后，研究表明，对于扑翼在悬停状态下，由于不均匀的下洗效应，采用弧弦分布可以将k降低到1.02。对于基于beta分布的形态逼真的机翼形状，表明在40%翼长时，翼面积第一力矩半径可达到1.07。
An analytical treatment to quantify the losses captured in the induced power factor, k, is provided for flapping wings in normal hover, including the effects of non-uniform downwash, tip losses and finite flapping amplitude. The method is based on a novel combination of actuator disc and lifting line blade theories that also takes into account the effect of advance ratio. The model has been evaluated against experimental results from the literature and qualitative agreement obtained for the effect of advance ratio on the lift coefficient of revolving wings. Comparison with quantitative experimental data for the circulation as a function of span for a fruitfly wing shows that the model is able to correctly predict the circulation shape of variation, including both the magnitude of the peak circulation and the rate of decay in circulation towards zero. An evaluation of the contributions to induced power factor in normal hover for eight insects is provided. It is also shown how Reynolds number can be accounted for in the induced power factor, and good agreement is obtained between predicted span efficiency as a function of Reynolds number and numerical results from the literature. Lastly, it is shown that for a flapping wing in hover k owing to the non-uniform downwash effect can be reduced to 1.02 using an arcsech chord distribution. For morphologically realistic wing shapes based on beta distributions, it is shown that a value of 1.07 can be achieved for a radius of first moment of wing area at 40% of wing length.