Jung Byung Kwon, Rezgui Djamel
School of Civil, Aerospace and Design Engineering, University of Bristol, Bristol BS8 1TR, UK.
R Soc Open Sci. 2024 Sep 30;11(9):240758. doi: 10.1098/rsos.240758. eCollection 2024 Sep.
Using their light wing and through the use of a leading-edge vortex (LEV), autorotating samaras can generate high lift while descending at extremely low speeds. But the flight performance of the samara, with respect to the wide design envelope, is still not well understood. Therefore, this paper aims to experimentally assess how the flight performance of three natural samara wings varies with differing wind speeds and flight conditions. The tests were conducted within a vertical wind tunnel and a novel rig was devised to effectively measure the vertical thrust and rotational rate of the autorotating samara at near frictionless conditions. Furthermore, a bespoke hub was implemented to control the coning and pitch angles of the samara wing. The tests generated a novel and comprehensive set of experimental data of autorotating samaras with changing wind speed, coning and pitch angles. The results also revealed that coning angles between 5 and 15 degrees can increase the vertical thrust produced by the samara by up to a maximum of . Additionally, it was found that samaras operate at extremely low pitch angles between -0.7 and -2.6 degrees to maximise their thrust, even though the conditions are close to the autorotational stability boundary.
通过其轻薄的翅膀并利用前缘涡流（LEV），正在自转的翅果在极低速下降时能够产生高升力。但是，就广泛的设计范围而言，翅果的飞行性能仍未得到很好的理解。因此，本文旨在通过实验评估三种天然翅果翅膀的飞行性能如何随不同风速和飞行条件而变化。测试在垂直风洞中进行，并设计了一种新颖的装置，以在接近无摩擦的条件下有效测量自转翅果的垂直推力和旋转速率。此外，还采用了定制的轮毂来控制翅果翅膀的圆锥角和俯仰角。这些测试生成了一组新颖且全面的关于自转翅果随风速、圆锥角和俯仰角变化的实验数据。结果还表明，5至15度之间的圆锥角可使翅果产生的垂直推力增加最多可达 。此外，还发现翅果在-0.7至-2.6度之间的极低俯仰角下运行以最大化其推力，尽管这些条件接近自转稳定性边界。
