影响振荡射流分离控制效果的关键因素

Key factors affecting the separation control effect of oscillating jets

为找出影响振荡射流对流场分离控制效果的关键因素,采用典型振荡射流激励器对偏转襟翼流场施加控制,通过数值模拟分析施加控制后的流场特点,总结了射流停滞的原因和影响;并对比不同扩张段、脉冲式和扫掠式振荡射流的控制效果,总结了射流扫掠范围对控制效果的影响。结果表明:射流向流场中传递动量的均匀程度和扫掠范围是影响控制效果的关键因素。射流向流场中传递动量越均匀,扫掠范围越大,则控制效果越好。激励器喉道过小会抑制射流偏转,使射流在出口两侧停滞,导致射流向流场中传递动量不均匀,因此偏转襟翼两侧的控制效果好于中部;增大扩张段会增大射流扫掠范围从而改善控制效果;脉冲式激励器内的尖劈会阻挡射流扫掠至其后方,导致射流扫掠范围小,偏转襟翼中部控制效果差。

Even though the oscillating jet actuator has been widely utilized in flow control,its control mechanism still requires substantial fundamental research.This paper conducted numerical simulations on controlling separated flow fields around a deflection flap using several oscillating jet actuators to identify the key factors affecting the control effect.By studying the control effect of different expansion sections and comparing the control characteristics of pulse and sweep oscillating jets,the causes and effects of jet stagnation and the influence of the jet's sweeping extent on the control effect are summarized.The results show that the uniformity of the momentum transferred by the jet into the flow field and the sweeping extent are the key factors affecting the control effect.A more uniform momentum transferred by the jet into the flow field and a larger sweeping extent yield a better control effect.If the actuator throat is too small,the jet will stagnate on both sides of the outlet due to a restrained deflection.This results in the uneven momentum transfer from the jet into the flow field and a better control effect on both sides of the deflected flap than that in the middle.Increasing the expansion section will increase the sweeping extent of the jet and improve the control effect.The wedge in the pulse exciter prevents the jet from sweeping to its rear,yielding a small sweeping extent of the jet and a worse control effect in the middle of the deflected flap.