OPPOSING PLASMA SYNTHETIC JET FOR LOW-SPEED FLOW SEPARATION INHIBITION

The plasma synthetic jet is a comprehensive high-energy excitation with a strong ability to restrain flow separation. This paper uses experimental and numerical simulation methods to investigate the inhibition of flow separation by plasma synthetic jets on a low-speed airfoil. The actuator's electrodes are built into the wing, and the injection holes are located at the leading-edge point. The smoke particle concentration distribution and the numerical simulation results show that the opposing plasma synthetic jet can move the flow separation point of the low-speed airfoil and improve the lift characteristics of the airfoil. The ability of the opposing plasma synthetic jet to drive the separation point distance and enhance the airfoil's lift characteristics will increase with the angle of attack. At an angle of attack of 16°, plasma actuation pushes the distance of the airfoil flow separation point to about 16.5% of the chord length, increasing the airfoil's lift coefficient by about 17.3%. The results show that in the low-velocity flow, the thermal jet generated by the opposing plasma synthetic jet interacts with the mainstream to form a strip-like thermal structure. The strip-shaped thermal structure has a leading mixing effect, which can enhance the mixing of the mainstream and the fluid in the separated shear layer. The jet body has a mixing-inducing impact, which can induce the dynamic re-attachment of the separated shear layer. The interaction between the strip-like thermal structure and the mainstream and between the jet body and the mainstream are the primary mechanisms for the opposing plasma synthetic jet to inhibit the flow separation of the low-speed airfoil and improve the lift characteristics of the airfoil. The strip-like thermal structure acts differently from the jet body at different stages. The difference leads to the change in their coupling and makes the lift characteristics of the airfoil appear in five typical phases. In addition, the experimental results also show that when the discharge parameters are constant, the flow control effect of the serial array actuator is more potent than that of a single actuator.