微型飞机机翼流动结构的数值研究

Numerical study of the flow structure around the wing of a micro air vehicle

通过数值求解非定常不可压N-S方程,研究微型飞机的小展弦比机翼在低Reynolds数下的流动特征。研究对象是展弦比为1.33,截面形状为E-174翼型的椭圆形机翼。数值模拟的Re=1×104,迎角为0°～45°。结果表明:从0°到10°迎角,机翼附近的流场是两侧对称的;迎角大于11°,流动变为两侧不对称。这个现象的出现是由于翼尖涡和机翼上表面的二次分离涡相互作用,使翼尖涡发生失稳。由于粘性作用,在整个迎角范围内气流发生分离。迎角小于33°,分离涡从机翼的上表面不断脱落;迎角大于33°,分离涡保持在机翼的背风面,形成驻涡现象。

The unsteady flow characteristics of the low-aspect-ratio wing of a micro air vehicle, especially relative to the tip vortices, were studied by numerically solving the unsteady incompressible Navier-Stokes equations. An elliptic planform wing with an aspect ratio of 1.33 using the E-174 airfoil was studied at Re =1×104 and angles of attack from 0° to 45°. The numerical results show that the flow around the wing is bilaterally symmetric for angles of attack from 0° to 10°. At angles of attack larger than 11°, the flow becomes bilaterally asymmetric. This phenomenon is caused by interaction between the secondary separation vortices on the upper surface of the wing and the tip vortices. Separation takes place for all angles of attack in this paper because of effect of viscosity. At angles of attack less than 33°, the primary separation vortices above the wing shed downstream; while at angles larger than 33°, the primary separation vortices stay above the wing lee side, forming a stationary vortex.