基于合成射流的旋翼翼型动态失速控制研究

针对直升机旋翼工作环境下来流速度和迎角(Angle of attack,AoA)耦合引起的动态失速问题,建立了基于合成射流的旋翼动态失速控制的数值模拟方法。采用运动嵌套网格方法,通过对翼型的平移和旋转实现变来流速度-变迎角的耦合。以积分形式的雷诺平均N-S方程为主控方程,空间离散使用Roe格式,时间离散为隐式LU-SGS方法,以OA209翼型为研究对象,在翼型上表面放置合成射流激振器,开展了射流位置、动量系数、无量纲频率以及偏角等参数对轻度失速、深度失速下翼型动态失速控制的研究。研究发现,轻度失速下,射流位置靠近气流分离点时(20%c附近,c为翼型弦长),对逆压梯度引起的轻度失速控制效果最佳。深度失速下气流分离点虽在5%c之前,但射流位于前缘分离泡后端(10%c附近)时控制效果较好。大迎角需要较大的动量系数才能有效控制。射流频率对涡结构的尺寸和数量会产生一定影响,能改变气动特性波动幅度。较小的射流偏角对轻度失速的控制更有效,而深度失速则需要较大的偏角。

Rotor Airfoil Dynamic Stall Control Based on Synthetic Jet

A numerical simulation method of rotor dynamic stall control based on synthetic jet is developed to solve the dynamic stall caused by coupling of flow velocity and angle of attack(AoA). This method is realized by the translation and rotation of the two-dimensional airfoil. Reynolds N-S equation in integral form is taken as the main control equation. Roeformat is used for spatial discrealization and implicit LU-SGS method for temporal discrealization. Taking the OA209 airfoil as the object, the synthetic jet excimer is placed on the upper surface of the airfoil, and the study on the dynamic stall control of airfoil with slight and deep stall is carried out with the parameters of jet position, momentum coefficient, dimensionless frequency and angle. It is found that under slight stall, when the jet position is close to the flow separation point (around 20%c), the control effect of slight stall caused by adverse pressure gradient is the best. Although the separation point of airflow under deep stall is before 5% c, the control effect is better when the jet is located behind the leading edge separation bubble (near 10% c). High angle of attack requires large momentum coefficient. The frequency has a certain influence on the size and number of vortexes and changes the fluctuation range of aerodynamic characteristics. Small angle of jet is more effective to control slight stall, while deep stall requires large angle.