合成双射流对下游声压级影响试验

Experiment on Effect of Dual Synthetic Jet on Downstream Sound Pressure Level

在Ma=0.4的来流条件下,利用安装在主翼后缘处的合成双射流激励器对襟翼上的流动进行控制,在风洞中开展了合成双射流对下游声压级影响的研究.基于脉动压力测量结果,结合油流显示试验,得到了合成双射流对下游不同流动状态区域声压级影响的一些结论.对于附着流,在其峰值频率附近激励会明显提高其声压级;对于受旋涡主导的流动,恰当的合成双射流控制可以降低声压级,激励频率较为关键.在俯仰运动过程中,对于附着流,激励提高了声压级,但不改变其迟滞特性;对于受旋涡主导的流动,激励对声压级的影响与攻角有关,能够减弱其迟滞特性,但激励强度对迟滞特性的影响较小,减小声压级的最佳激励与运动历程有关.

Experimental investigation on the effect of dual synthetic jet on downstream sound pressure level(SPL)was conducted in a wind tunnel with free stream velocity of Ma=0.4.Dual synthetic jet actuators placed around the trailing edge of the main wing were utilized to control the flow over the flap.Based on the results of pulsating pressure measurement and oil-flow visualization,some conclusions about the control effect on SPL with different flow states were obtained.For an attached flow,the SPL is evidently enhanced by actuation with peak frequency of the initial flow.For a vortex-dominated flow,an appropriate actuation can reduce the SPL and the frequency is an important factor.During a pitching motion,actuation enhances the SPL of the attached flow but does not affect the hysteresis of SPL.While for the vortex-dominated flow,the influence of actuation on SPL is related with angles of attack,and the hysteresis of SPL is weakened.However,the actuation strength has minor impact on the variation of hysteresis.It seems that the optimal actuation for noise reduction has to do with the course of movement.