This paper shows an experimental result of delayed feedback flow control around a NACA0015 airfoil using plasma synthetic jet actuator (PSJA). Delayed feedback control (DFC) method is employed to reduce separation by stabilizing the periodic behavior of wake flow induced by PSJA. We configure a DFC system for switching on and off of the PWM signal voltage based on the flow velocity. First, we examined the separation reduction effect by changing delay time r on NACA0015 fixed at 15 deg angle of attack. Depending on t, the drinving by the DFC increases higher velocity than the case of continuous driving or burst-wave driving. In the case of τ = 4 ms, the power significantly decreased at the natural frequency of the wake flow. In the case of r = 30 ms, the power of the characteristic frequency was emphasized similarly to the burst-wave driving. Therefore, we experimentally succeeded in changing the frequency characteristics of the flow by DFC. Second, we confirmed separation reduction by DFC based on flow velocity distribution and turbulence distribution. This experiment compared the differences in flow effects caused by the τ = 4 ms and 30 ms. There is no difference in the flow velocity distribution and the RMS distribution among different r. We focused on the driving ratio of the PWM signal and degree of increase in the flow velocity. In the case of r = 4 ms, the drinving time is about 5% less than the case of τ = 30 ms, although the flow velocity increases. In other words, it is possible for DFC to contribute considerably to reduced power consumption and increase in the flow velocity.
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