攻角拉起时前体非对称涡诱导机翼摇滚运动

针对目前前体非对称涡诱导机翼摇滚研究时攻角往往处于静态而没有考虑攻角动态拉起的问题,在北航D4风洞中采用细长旋成体与30°后掠翼的组合体模型,通过不同拉起速度下的机翼摇滚运动实验,分析了攻角拉起速度对前体非对称涡诱导机翼摇滚运动的影响及影响产生的原因;随后通过在快速拉起摇滚运动过程中进行模型表面压力测量,研究了快速拉起机翼摇滚的流动机理.实验结果表明,由于机翼摇滚运动的时间随攻角拉起速度增加而减少,使得在3个不同的拉起速度分区内,摇滚运动呈现为不同的运动形态,其中第3个快速拉起分区内的摇滚运动为与攻角静态时完全不同的类正弦摇滚运动形态.与攻角静态时机翼摇滚的流动机理不同,快速拉起时这种类正弦摇滚运动主要源于前体非对称涡随攻角的演化,前体非对称涡随滚转角的涡型切换不再重要. 

Wing rock motion induced by forebody asymmetric vortices in pitch-up

Aiming to the issue that the angle of attack was usually fixed rather than pitched-up in the previous researches about the wing rock induced by forebody asymmetric vortices, series of wind tunnel experiments were conducted in Beihang University D4 wind tunnel over the configuration of a pointed ogive-cylindrical body with 30° swept wings. Effect of pitch rate on wing rock motion as well as the mechanism of that was first studied through wing rock experiments in different pitch rates. The flow mechanism of wing rock in high rate pitch-up was then studied through the surface pressure measurements during the dynamic wing rock. Experimental results show that, as the wing rock motion time reduces with increase of pitch rate, the motion patterns of wing rock are different in three different intervals of pitch rate. The sinusoidal-like motion, which is totally different from the motion at static angle of attack, would occur in the third interval with high rate pitch-up. The variation of forebody flow with angle of attack, instead of the variation of forebody flow with roll angle, is found to be responsible for the sinusoidal-like motion in high rate pitch-up. Hence, the flow mechanism of wing rock in pitch-up is greatly different from that at static angle of attack.