抄録
The present study focuses on the multiple separation-control mechanisms of burst actuation with a dielectric barrier discharge plasma actuator. Control of separated flow around a NACA 0015 airfoil at the Reynolds number of 63,000 is investigated using a plasma actuator mounted at 5% chord length from the leading edge. A parametric study on burst frequency and input voltage are conducted on three post-stall angles of attack using time-averaged pressure measurements and time-resolved particle imaging velocimetry (PIV). The trailing edge pressure is chosen as the index of separation control and indicates that the optimum burst frequency is different for each angle of attack. Several flow fields are discussed in detail and two flow-control mechanisms are clarified: the utilization of a large vortex and promotion of turbulent transition. With regard to the first mechanism, the phase-lock PIV indicates that a vortex structure, the size of which increases as the burst frequency decreases in this experimental range, is shed from the shear layer for each burst actuation. With regard to the second mechanism, time-averaged pressure and PIV measurements reveal that burst frequency of F^+ = 6-10 has the capability to promote turbulent transition. At higher angle of attack, only the utilization of a large vortex structure is effective for separation control, whereas, near the stall angle, the promotion of turbulent transition provides better separation control.
