Effect of burst frequency and reynolds number on flow control authority of DBD plasma actuator on NACA0012 Airfoil

This paper discusses the effects of two parameters on flow control by dielectric barrier discharge (DBD) plasma actuator: 1) Burst frequency and 2) Reynolds number. Experiments were conducted in a low speed wind tunnel using a NACA0012 airfoil with the plasma actuator located on the leading edge. The dimensionless burst frequency F⁺ (hereafter noted as burst frequency) was varied from 0.5 to 7 while the experiments were performed at Reynolds number of 31,500, 63,000, and 126,000 (corresponding to freestream velocity of 5m/s, 10m/s, and 20m/s, respectively). At stall angle, there is a small increase in lift which seems to be independent of the burst frequency. In deep stall condition, the effects of burst frequency is clearly discernible where increment of the burst frequency results in the loss of lift for all Reynolds number conditions. However, the presence of superior suction peak on the pressure distribution for high burst frequency cases suggest that they are more effective at controlling the flow compared to low burst frequency cases. Additionally, we highlight the effect of the Reynolds number on the control capability on two representative burst frequency cases of 1 and 7. It was found that high freestream velocity promoted better flow control, in the form of a stronger suction peak, if the baseline flow is significantly attached. However, in deep stall condition, momentum addition becomes the dominant phenomenon. We furthered increased the direct momentum addition through the augmentation of input voltage V_p-p and burst ratio BR. For both types of momentum addition, high burst frequency actuation proved to be more sensitive than lower burst frequency actuation in deep stall condition. Increment of input voltage greatly improved control authority but for burst ratio, degradation of control performance was seen when it was increased. We compliment our findings with numerical simulations to gain a better understanding.