合成射流对失速状态下翼型大分离流动控制的试验研究

为研究低速状态合成射流在抑制翼型气流分离和推迟失速方面的控制机理, 开展了NACA0021 翼型失速特性射流控制的风洞试验研究. 通过系统性的模型测力、翼型瞬态流场粒子图像测速和边界层速度测定的对比试验, 深入探索了合成射流各参数对翼型失速特性控制效果的影响规律. 试验结果表明射流偏角在翼型升力和失速迎角控制方面的效果对射流动量系数较为敏感: 当动量系数较大时, 近切向射流的控制效果更好. 射流动量系数为0.033 时, 偏角30°的射流使得翼型升力系数峰值提高23.56%, 失速迎角增大5°; 而动量系数较小时, 偏角较大的射流能够获得最佳控制效果. 射流动量系数为0.0026 时, 法向射流对翼型最大升力系数控制效果最好(提高9.2%). 

EXPERIMENTAL INVESTIGATION OF SYNTHETIC JET CONTROL ON LARGE FLOW SEPARATION OF AIRFOIL DURING STALL

In order to investigate the active flow control effect of synthetic jet on preventing flow separation and delaying stall of airfoil at low speed, wind-tunnel tests of jet control on the stall characteristics of NACA0021 airfoil are conducted. By systematic comparison tests including measurements about model aerodynamic forces, flow velocity on the airfoil upper surface based on Particle Image Velocimetry (PIV) technology and velocity profiles in boundary layer, the influences of synthetic jet parameters on control effects of airfoil stall characteristics are further explored. A large number of experimental results indicate that control effects on airfoil lift and stall angle of attack (AoA) due to jet angle are sensitive to the momentum coeffcient of synthetic jet. Overall, the control effects of the almost tangential jet are more effective when the momentum coeffcient of synthetic jet is large enough: increments about 23.6% of maximum lift coeffcient and 5° of stall-incidence of airfoil are obtained when the jet angle is 30° with jet momentum coeffcient being 0.033. On the other hand, a larger jet angle is required to achieve the best control effect when the momentum coeffcient is small: when the momentum coeffcient is about 0.0026, the normal jet is most effective on increasing the maximum lift coeffcient of airfoil by an increment about 9.2%.