来流局部干扰对三角翼气动特性的影响

通过在三角翼上游加入干扰圆柱的风洞实验方法,研究了来流干扰对微小型飞行器MAV(Micro Air Vehicle)气动特性的影响.结果表明,在刚性和弹性三角翼顶点上游加入圆柱干扰时,两者均出现缓失速,刚性翼产生缓失速与干扰圆柱尾流关系密切,弹性翼的缓失速不仅与此有关,还与弹性翼的振动有关.无干扰或在机翼顶点加入干扰时,在攻角为4°~18°内弹性翼的升力系数比刚性翼的要大,但升阻比相对要小.由于弹性翼的振动与机翼绕流结构、气动力之间的耦合,弹性翼顶点与翼尖振动的主频随着攻角增大呈规律性的变化,失速攻角附近翼尖的振动主频是其涡脱落频率. 

Effects of free stream local disturbance on delta wing aerodynamics

The effects of free stream disturbance on micro air vehicle (MAV) aerodynamics was investigated using delta wings with disturbance introduced by an upstream cylinder in wind tunnel. The results indicate that the stall-delay happen when disturbance is introduced in the upstream of apex for both rigid and flexible delta wings, the stall-delay of rigid wing relates with wake flow of disturbing cylinder, the stall-delay for flexible wing not only relates with this but also with its vibration. Without disturbance or the disturbance introduced in the upstream of wing apex, the lift coefficient of flexible wing is larger than that of rigid one when attack angle is in the range of 4° to 18°, but the corresponding lift to drag ratio of flexible wing is smaller than that of rigid one. Because of the coupling among the vibrations of flexible wing, the flow structure and the aerodynamics, the dominant frequencies of flexible wing-s apex and tip vibration were changed regularly with the sweep angle increases. The dominant frequency of vibration for flexible wing tip is frequency of vortex shedding around stall angle.