Flow control over swept wings using nanosecond-pulse plasma actuator

An experimental study aiming at lift enhancement of a swept wing by using a plasma actuation driven by repetitive nanosecond-pulse voltage was carried out. The periodic plasma actuation was applied near the apex in order to manipulate the leading edge vortices in the post-stall regime. Wind-tunnel tests using a full-span wing model were conducted for various angles of attack α at a Reynolds number Re≡CmU∞/ν=6.0×105, which was based on the effective chord length Cm and freestream velocity U∞. The repetitive frequency of plasma excitation f was also varied from 20 Hz to 1000 Hz. The aerodynamic forces and moments were obtained as a function of α and f by means of a six component balance. The forces and moments were also compared from asymmetric and symmetric actuation configurations point of view: actuations on one side and on both sides of the leading edges. The increase of the time-averaged lift coefficient CL¯ from 0.807 to 0.842 was observed when the symmetric actuation was applied at the reduced frequency of F+≡fCm/U∞≈0.86. The increase of the lift coefficient was strongly correlated with the increase of drag and pitch-up. The frequency dependency of the lift increase was affected by α. Also, the frequency dependency was changed if asymmetric actuation on a leading edge was applied. The velocity field in the wake was measured by means of stereoscopic particle image velocimetry and was evaluated based on control volume analysis. The results indicated that the change in the intensity of the streamwise vortex led to the lift enhancement.