摘要
介绍了在装有液体的有机玻璃容器中进行的二维平板翼作悬停拍翼运动的流场显示实验.研究了低雷诺数运动下,仰俯旋转过程中不同的转动角速度,匀速平动阶段不同的水平攻角分别对流场结构的影响以及超前、对称、滞后三种相位模式下的涡流场结构.实验结果表明:挥拍过程中翼后缘的涡层不断地脱泻,前缘涡不断发展并附着在翼面是翼型产生高升力的重要机制;匀速平动阶段前缘涡的形成附着与水平攻角有关,攻角过小不易产生前缘涡,攻角过大则易使前缘涡与翼面分离;翼型的上仰过程使前缘涡得到加强,这对升力的产生有一定的贡献;三种相位下的涡流场形态各有不同,上挥(下拍)初期前缘涡的运动主要存在两种形态.
An experimental study of flapping wing motion was conducted in a 2-D model test system. DPIV based flow visualization was carried out to examine the vortex field around the flapping wing, whose motion is at a low Reynolds number. The experiments were conducted for various controlling parameters, such as different sweeping velocities, supination/pronation rotational speeds and angels of attack, as well as the three phase motion patterns, namely, advance, symmetry and delay patterns. It was found that the trailingedge vortex is washed away continuously into the wake flow during the stroke, and the leading-edge vortex attached to the foil surface, which is the main mechanism for the generation of lift force. During the uniform stroke motion stage, no leading-edge vortex was observed for those cases in which angles of attack are below 15°. The leading-edge vortex is formed obviously and attached to the wing surface when the angles of attack are between 30° and 50°. If the angle of attack is above 50°the leading-edge vortex will be quickly formed and separated from the wing surface soon after the formation. The flow fields are different for the three phase motion patterns and there are two types of leading-edge vortex motion at an earlier stage of upstroke or downstroke.
基金
中国科学院创新项目(KJCXSWL2
KJCXSWL04)资助.
关键词
悬停
拍翼运动
涡动力学
流动显示
hovering
flapping wing motion
vortex dynamics
flow visualization
