直接测力俯仰振荡翼型动态气动性能研究

STUDY ON DYNAMIC AERODYNAMIC PERFORMANCE OF PITCH OSCILLATING AIRFOIL WITH DIRECT FORCE MEASUREMENT

在西北工业大学NF-3低速风洞二元实验段开展翼型俯仰振荡运动动态气动性能深入研究。实验模型为展向三段式测力模型,测力仅在模型中段进行以减小风洞侧壁干扰的影响。实验中采集模型的转动瞬态迎角、计算模型中段的惯性力和惯性力矩、并从天平采集数据中扣除以修正模型惯性对结果的影响。结果表明,迎角超过正向或负向静态失速迎角是升力系数和俯仰力矩系数产生大的迟滞环的必要条件。随着振荡缩减频率增大,动态失速会推迟,升力系数迟滞环增大,阻力系数增大,最大迎角附近的俯仰力矩系数减小。在迎角小于静态失速迎角或超过不大的迎角范围,随着缩减频率的增大,翼型振荡运动俯仰力矩系数上行时减小,下行时增大。随着振荡振幅的增大,翼型振荡运动动态升力系数和俯仰力矩系数的迟滞环增大。随着平均迎角的增大,翼型迎角更多地进入正向失速区,升力系数迟滞环增大,俯仰力矩系数最小值变小。雷诺数对升力系数、阻力系数和俯仰力矩系数迟滞环无明显影响;但是,在翼型模型下行过程,随着雷诺数的增大,升力恢复提前,同时迟滞环随雷诺数增大而减小。

An in-depth study on the dynamic aerodynamic performance of the pitch oscillating airfoil is carried out in the twodimensional test section of the NF-3 low-speed wind tunnel of Northwestern Polytechnical University. The test model is a span-wise threesection force measurement model,and the force measurement is only performed in the middle section of the model to reduce the influence of the sidewall interference of the wind tunnel. In the experiment,the transient angle of attack of the model is collected;the inertial force and pitch moment on the middle section of the model are calculated and subtracted from the data collected by the balance to correct the influence of the model’s inertia on the results. The results show that the angle of attack exceeding the positive or negative static stall angles of attack is a necessary condition for the lift and pitch moment coefficients to produce a large hysteresis loops. As the oscillation reduced frequency increases,the dynamic stall is delayed,the lift coefficient hysteresis loop increases,the drag coefficient increases,and the pitch moment coefficient near the maximum angle of attack decreases. When the angle of attack is less than the static angle of attack of stall or exceeds a small range,with the increase of the reduced frequency of the airfoil oscillation,the pitch moment coefficient of the airfoil decreases when it goes up and increases when it goes down. With the increase of the oscillation amplitude,the hysteresis loops of both dynamic lift coefficient and pitch moment coefficient of the oscillating airfoil increase. As the average angle of attack increases,the angle of attack of airfoil enters the positive stall zone more,the lift coefficient hysteresis loop increases,and the minimum pitch moment coefficient decreases. The Reynolds number has no obvious effect on the hysteresis loop of lift,drag and pitch moment coefficients;however,in the downward process,as the Reynolds number increases,the lift recovery advances,and the hysteresis loop decreases.