Researches On Vectoring Dual Synthetic Jet With All-electric Control And Self-sustaining Dual Synthetic Jet Applications In Supersonic Flow Field

With the advantage of flexible and controllable,active flow control has an extensive prospect in future researches of fluid mechanics.As a kind of active flow control technology,Dual synthetic jet(DSJ)actuator has been widely used.However,it has some intrinsic shortcomings,for instance,the existing vector control method is complicated,the response is slow,and the power of DSJ is not strong enough.In order to improve the control range of the DSJ,a new DSJ vector control method is proposed base on asymmetrical electric signal.For the supersonic flow field control,a self-sustaining DSJ which can use the flow field characteristic is designed.The vectoring characteristics of DSJ actuator can be realized by inputting asymmetrical electric signal,which makes DSJ actuator a wider application in the active flow control.The effects of different waveform signals and driving parameters(voltage and frequency)on DSJ actuator are studied by particle image velocimetry(PIV)experiment.The results show that the DSJ deflects under designed electric signal.In the same cycle,the trend of vectoring angle increases at first and then decreases with the increase of duty cycle,and there exists an optimal duty cycle making the maximum deflection of DSJ.Besides,the vectoring deflection with the driving voltage changes is similar to that of duty cycle.For the driving frequency,there is a minimum vectoring angle near the resonance frequency of the vibrating diaphragm.Using the numerical simulation,the changes of pressure and vorticity of the flow field are obtained,and the mechanism of the deflection is also discussed.To enhance the mixing characteristic of cavity with mainstream in the scramjet engine,two types of self-sustaining DSJ were used to enhance the mass exchange of the cavity.One of self-sustaining DSJ actuators utilizes the pressure of shock;the other is using ram-air.Under the same conditions,the former has a more powerful control effect,and the improvement of mass exchange is more notable.In addition,The position of the actuator' outlet has a great influence on the control effect.For the selected cavity with L/D=3.88,the mass exchange rate can be improved by 49.2% when the position of outlet is located in the middle of cavity floor.Besides,cavity configurations and Mach numbers can also make a difference to the mixing characteristic.The results suggest that the cavity with a longer L/D can obtain a better control effect when using self-sustaining dual synthetic jet actuator,and the mass exchange rate of cavity with L/D=7.76 can be increased by 115%.For the same cavity,the mass exchange rate is improved when increasing the fluid velocity.Self-sustaining DSJ is applied to the shock control of supersonic compression corner.In the wind tunnel with the flow of Mach 5,the flow field is observed by the high-speed shadowing.The results show that self-sustaining DSJ can effectively control the shock of wedge.The strength of the self-sustaining DSJ increase with the increase of the inlet size,and the pressure of the wedge surface decreases as the inlet size increases.But when changing frequencies of the membrane,the control effects are not so obvious.