Muir Rowan Eveline, Arredondo-Galeana Abel, Viola Ignazio Maria
Institute for Energy Systems, School of Engineering, University of Edinburgh, Edinburgh, UK.
R Soc Open Sci. 2017 Aug 23;4(8):170077. doi: 10.1098/rsos.170077. eCollection 2017 Aug.
Recent investigations on the aerodynamics of natural fliers have illuminated the significance of the leading-edge vortex (LEV) for lift generation in a variety of flight conditions. A well-documented example of an LEV is that generated by aircraft with highly swept, delta-shaped wings. While the wing aerodynamics of a manoeuvring aircraft, a bird gliding and a bird in flapping flight vary significantly, it is believed that this existing knowledge can serve to add understanding to the complex aerodynamics of natural fliers. In this investigation, a model non-slender delta-shaped wing with a sharp leading edge is tested at low Reynolds number, along with a delta wing of the same design, but with a modified trailing edge inspired by the wing of a common swift . The effect of the tapering swift wing on LEV development and stability is compared with the flow structure over the unmodified delta wing model through particle image velocimetry. For the first time, a leading-edge vortex system consisting of a dual or triple LEV is recorded on a swift wing-shaped delta wing, where such a system is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds number or angle of attack. These findings suggest that the trailing-edge geometry of the swift wing alone does not prevent the common swift from generating an LEV system comparable with that of a delta-shaped wing.
近期对天然飞行者空气动力学的研究揭示了前缘涡（LEV）在各种飞行条件下对升力产生的重要性。一个有充分记录的前缘涡例子是由具有大后掠角、三角形机翼的飞机产生的。虽然机动飞机、滑翔鸟类和扑翼飞行鸟类的机翼空气动力学有很大差异，但人们认为现有知识有助于增进对天然飞行者复杂空气动力学的理解。在这项研究中，一个具有尖锐前缘的非细长三角形机翼模型在低雷诺数下进行了测试，同时还测试了一个相同设计的三角形机翼，但后缘经过修改，灵感来源于普通雨燕的翅膀。通过粒子图像测速技术，将逐渐变细的雨燕翅膀对前缘涡发展和稳定性的影响与未修改的三角形机翼模型上的流动结构进行了比较。首次在雨燕翅膀形状的三角形机翼上记录到了由双前缘涡或三前缘涡组成的前缘涡系统，并且在所有测试条件下都发现了这样的系统。结果表明，前缘涡破裂的展向位置由局部弦长决定，而不是由雷诺数或攻角决定。这些发现表明，仅雨燕翅膀的后缘几何形状并不能阻止普通雨燕产生与三角形机翼相当的前缘涡系统。
