摘要:
采用倾斜出口合成射流激励器对NACA633-421三维直机翼进行分离流主动流动控制,天平测力结果表明合成射流可以有效地控制机翼流动分离,提升最大升力系数10.4%,推迟失速迎角4°。运用边界层测试技术及粒子图像测速系统(PIV)对合成射流分离流控制机制进行研究分析,结果表明,控制后边界层速度型变得“饱满”,形状因子减小,其底层能量增加,抵抗逆压梯度能力增强。瞬态及时均化PIV测试流场图进一步证明合成射流向主流进行动量注入及掺混后,主流附着机翼表面,翼面附近流体湍流动能和雷诺剪切应力增加,分离点向下游推迟,流动分离得到抑制。
Abstract:
Active flow control on a three-dimensional NACA633-421 airfoil has been investiga-ted experimentally using beveled-slit-synthetic-j et-actuator (BSSJA).Balance force measurement results show that the synthetic jet can control the flow separation effectively,improve the maxi-mum lift coefficient by 10.4% and increase the stall angle of attack by 4°.Both boundary layer velocity measurement and particle image velocimetry (PIV)technology have been performed un-der selected experimental conditions to investigate the mechanism of synthetic jet flow control. Results reveal that the shape factor of boundary layer velocity profile decreases with BSSJA con-trol and the promotion of the power of the boundary layer is responsible for the control effect. The instantaneous flow maps and ensemble-averaged PIV results reveal that synthetic j et tends to enhance the flow dilution and transfer the mass flux so that the separated flow could attach to the wall of NACA633-421 airfoil again.In addition,the turbulent kinetic energy (TKE)and Reyn-olds stress are increased near the wall compared to the situation without control.
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