Turbulent Boundary Layer Control by Plasma Synthetic Jet Actuator aiming Engineering Application

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Several Plasma Synthetic Jet Actuators (PSJA) were made and tested to examine flow induction characteristics affected by their geometry. We found that optimal width ratio of Anode and Cathode exists in order to maximize the flow velocity induced by the actuator. Effects of PSJA on plane turbulent boundary layer were measured by Direct Shear Stress Sensor and Hot-wire Anemonetry in low speed and low turburence wind tunnel. As results, we proved that PSJA reduces shear stress at the downstream of the actuator. This shear stress reduction phenomenon is measured directly at the first time in this study, and is significant for engineering applications. However, the shear stress reduction effects observed only in the vicinity of the actuator. Shear stress was increased as goes downstream from the actuator.Computational Fluid Dynamics (CFD) studies conducted to investigate the flow fields induced by the PSJA. Compressible flow analysis considering dielectric body force clearly showed how PSJA … More induces jet flow. And we also found that vacuum dielectric coefficient can be used to simulate induced flow in sufficient quantitative accuracy.Closed loop feedback control was tested in order to improve the effectivity of the flow separation control on NACA012 airfoil. Delayed feedback control (DFC) method, using hotwire as a downstream sensor, was chosen because of its robustness to the control parameters. We found that DFC can reduce the power consumption needed to activate PSJA in half as compared to open loop control.Image Thermograph measurements were conducted to know how PSJA induces heat along with flow. In this study, glow discharge was generated using high voltage transformer and audio power amplifier. Because of significant phase shift between anode voltage and current, efficiency of the PSJA was not in satisfactory condition, in the sense that small portion of supplied electrical power as transformed into fluid flow. Temperature at downstream of PSJA often raised by 30 degree Celsius.Relative humidity effects also investigated in small channel using mass flow meter. The height of the channel was set to several times higher than the PSJA height. In conclusion, mass flow induced by PSJA tends to be decreased as relative humidity increases.We are planning to develop micro pumps and swirlers using PSJA. Less