低雷诺数仿生分离流翼型气动特性初探

Preliminary aerodynamic exploration for bioinspired separated flow airfoil at low Reynolds number

为了探索适合低雷诺数微型飞行器的翼型形式,基于对自然界鸟类和昆虫滑翔飞行时翅膀形状的观察,设计出一种由前缘削尖平板和后缘圆弧翼型组合而成的仿生分离流翼型。数值研究结果表明,气流在削尖平板的前缘点强制分离,形成大范围低压分离流动,随后在后部圆弧翼上表面再附形成稳定低压涡流区,从而实现较高的气动效率和较强的抵抗大气湍流的能力。上削尖平板可以使流动分离点固定在削尖点。相对于单独平板,仿生分离流翼型的升力系数有大幅提高,迎角为4°时提高了112%。此外,仿生分离流翼型可以在较宽的迎角范围内(4°~20°)保持高升力,但是迎角增加,阻力也快速增大,因此小迎角情况下(小于4°)气动效率更优。

In order to explore the type of airfoil suitable for low Reynolds number micro aerial vehicles,based on the observation of the wing shape of natural birds and insects during gliding flight in nature,a bioinspired separated flow airfoil composed of a sharpened leading edge flat plate and a circular arc airfoil was designed.Computational results demonstrated that the flow was forced to be separated at the sharp leading edge to generate low pressure flow and then be reattached at the upper surface of the rear arc airfoil to form stable low pressure vortical flow,thus high aerodynamic efficiency and strong turbulence resistance could be achieved.The separation could be fixed at the sharp leading edge point for upper-cropped flat plate.Compared with the single cropped flat plate,the lift coefficient of the bioinspired separated flow airfoil was improved significantly,by 112% at angle of attack 4°.In addition,the bioinspired separated flow airfoil can maintain high lift within a wide range of angle of attack between 4° and 20°,but the aerodynamic efficiency was higher at angles of attack lower than 4° because the drag increased rapidly with the increase of the angle of attack.