Unsteady aerodynamics of dragonfly using a simple wing–wing model from the perspective of a force decomposition
Unsteady aerodynamics of dragonfly using a simple wing–wing model from the perspective of a force decomposition
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DOI：
10.1017/s0022112010003484
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发表时间：
2010-11
影响因子：
3.7
通讯作者：
C. Hsieh;C. Kung;Chien-Cheng Chang;C. Chu
中科院分区：
文献类型：
--
作者：
C. Hsieh;C. Kung;Chien-Cheng Chang;C. Chu
昆虫在几十到几百赫兹的频率下执行它们的多种飞行技能，而这些技能的空气动力学基本上是不稳定的。直觉上，非定常性可能来自于非定常机翼运动、非定常表面涡量或被甩入后尾流和前尾流的涡量。在这项研究中，我们建议使用一个简化的机翼-机翼模型，从多体力分解和相关的力元素的角度来研究的空气动力学的机翼。昆虫的飞行通常在雷诺数为几百的数量级，在这一点上，表面涡量被证明起着重要的作用。在一些重要的情况下，附加的质量效应是不可忽略的。然而，对力的主要贡献来自流动内的涡量。本研究的重点是相互作用的影响，由于前，后翼之间的平移以及旋转运动的相位差。众所周知，动态失速涡是非定常机翼获得升力的重要机制。在分析升力和推力元件的寿命周期时，我们还将一些高升力和推力与被确定为“骑在”升力元件上、“被”推力元件驱动和“被”推力元件吸引的机制联系起来，通过这些机制，机翼分别利用了机翼下面、前面和后面的脱落或融合涡流。此外，附接到每个机翼的剪切层也可以提供显著的推力元件。
Insects perform their multitude of flight skills at frequencies of tens to hundreds of Hertz, and the aerodynamics of these skills are fundamentally unsteady. Intuitively, unsteadiness may come from unsteady wing motion, unsteady surface vorticity or vorticity being shed into the rear and front wakes. In this study, we propose to investigate the aerodynamics of dragonfly using a simplified wing–wing model from the perspective of many-body force decomposition and the associated force elements. Insect flight usually operates at Reynolds numbers of the order of several hundreds, at which the surface vorticity is shown to play a substantial role. There are important cases where the added mass effect is non-negligible. Nevertheless, the major contribution to the forces comes from the vorticity within the flow. This study focused on the effects of mutual interactions due to phase differences between the fore- and hindwings in the translational as well as rotational motions. It is well known that the dynamic stall vortex is an important mechanism for an unsteady wing to gain lift. In analysing the life cycles of lift and thrust elements, we also associate some high lift and thrust with the mechanisms identified as ‘riding on’ lift elements, ‘driven by’ thrust elements and ‘sucked by’ thrust elements, by which a wing makes use of a shed or fused vortex below, in front of, and behind it, respectively. In addition, a shear layer attaching to each wing may also provide significant thrust elements.