In this study, an experimental investigation of separation control using a dielectric barrier discharge plasma actuator was performed on an NACA0015 airfoil over a wide range of Reynolds numbers, angles of attack, and nondimensional burst frequencies. The range of the Reynolds number was based on a chord length ranging from 2.52 × 10${}^5$ to 1.008 × 10${}^6$. A plasma actuator was installed at the leading edge and driven by AC voltage. Burst mode (duty-cycle) actuation was applied, with the nondimensional burst frequency ranging between 0.1–30. The control authority was evaluated using the time-averaged distribution of the pressure coefficient $Cp$ and the calculated value of the lift coefficient $C_l$. The baseline flow fields were classified into three types: (1) leading-edge separation; (2) trailing-edge separation; and (3) the hysteresis between (1) and (2). The results of the actuated cases show that the control trends clearly depend on the differences in the separation conditions. In leading-edge separation, actuation with a burst frequency of approximately $F^{+}=$ 0.5 creates a wide negative pressure region on the suction-side surface, leading to an increase in the lift coefficient. In trailing-edge separation, several actuations alter the position of turbulent separation.

Plasma actuators are promising devices for near-wall flow control; however, conventional actuators often produce jets and forcing regions with excessive wall-normal spread, which reduces near-wall actuation selectivity. In this study, micro plasma actuator arrays with SDBD and pulsed-DC configurations were experimentally characterized to examine jets and forcing patterns confined closer to the wall. Micro actuator arrays consisting of eight integrated elements with sub-millimeter electrodes (0.5 mm exposed width) were fabricated by photolithography. Mean velocity fields were evaluated by conventional particle image velocimetry (PIV), while near-electrode flow structures were examined by single-pixel PIV. In addition, the streamwise body-force distribution was estimated from the high-spatial-resolution velocity fields. The results showed that the micro actuator arrays formed jets confined closer to the wall than the conventional actuators, with repeated re-acceleration along the electrode array. The estimated body-force distribution showed that the SDBD configuration retained a reverse-sign forcing pattern near the wall, whereas the pulsed-DC configuration formed a more concentrated near-wall positive forcing pattern with a weaker reverse-sign region and a lower positive peak location (0.54 mm, compared with 1.38 mm for the SDBD configuration). Under the tested quiescent-air characterization conditions, the pulsed-DC configuration produced a more wall-confined positive estimated-forcing pattern.