Research On Plasma Synthesis Jet And Its Application In Turbulence Drag Reduction

Flight drag is a key aerodynamic parameter to consider in aircraft design and can be classified into sources such as pressure drag,friction drag,and induced drag.Turbulent friction drag is the primary source of typical aircraft friction drag.Reducing turbulent friction drag can significantly increase aircraft range and endurance,reduce environmental pollution,and lower flight costs.Plasma actuation,with its advantages of low energy consumption and no complex auxiliary equipment,has broad prospects in aerospace engineering applications.Synthetic jet blowing offers fast frequency response and easy arrangement on the surface of control areas.This paper merges the advantages of both plasma actuators and synthetic jet blowing to design an annular synthetic jet plasma actuator suitable for turbulent drag reduction.First,to optimize the geometric configuration of the annular synthetic jet plasma actuator,a body force experimental platform,and a Schlieren experimental platform are built to diagnose the actuator comprehensively.Based on the results of body force and Schlieren experiments,optimization criteria for the actuator are proposed:the narrower the exposed electrode width,and the larger the covered electrode radius,the better the actuator performance.Next,under static atmospheric conditions,a two-dimensional PIV system is used to study the flow field evolution rules induced by steady-state and unsteady synthetic jet actuators.Experimental results show that as the steady-state actuation voltage increases,the maximum speed of the induced flow field also increases.Changing the carrier frequency around the optimal carrier frequency(10 kHz-13 kHz)does not significantly affect the flow field induced by the actuator.When applying unsteady actuation,the actuator generates induced vortices that gradually migrate along the y-axis with the main flow.Under the action of body force,the intensity of induced vortices gradually increases;when the body force disappears,viscosity dominates,and the intensity of induced vortices gradually decreases;induced vortices are generated in each discharge cycle,which is cyclical.Lastly,the control effects of the annular synthetic jet plasma actuator on turbulent boundary layer flow under different working conditions are studied through wind tunnel experiments.Experimental results show:when U∞=7m/s,applying steady-state actuation,the drag reduction effect gradually decreases with the increase of actuation voltage;when applying unsteady actuation,when the optimal frequency f+≈1,the drag reduction effect is 13.37%;under the optimal control parameters,steady-state actuation control is superior to unsteady actuation control;when Vpp=7 kV,the optimal local drag reduction rate of 17.72%is achieved;the experimental results are evaluated comprehensively,revealing the mechanism by which the annular synthetic jet plasma actuator induces wall friction drag changes in the turbulent boundary layer;discharge of synthetic jet actuator forms upwash and downwash in the boundary layer,upwash reduces the speed and speed fluctuation at the bottom of the boundary layer leading to drag reduction,while on the downwash side,it leads to increased drag.The intensity of plasma actuation must match the intensity of external flow to further enhance the drag reduction effect.