Multiple control modes of nanosecond-pulse-driven plasma-actuator evaluated by forces, static pressure, and PIV measurements

The control authority of a nanosecond-pulse-driven dielectric-barrier discharge plasma actuator (ns-DBDPA) was evaluated via wind tunnel experiments with the simultaneous measurement of lift and drag forces, pressure on the airfoil surface, and particle image velocimetry (PIV) measurements. In these experiments, a Reynolds number of Re = 2.6 × 10⁵ was applied with a freestream velocity of 40 m/s under atmospheric pressure. The force measurements revealed multiple peaks of lift force recovery and drag force modulation depending on the angle of attack, α, and non-dimensional frequency, F⁺. At the positive post-stall α close to stall α of approximately 16°, F⁺ values around 2.0 were effective for lift recovery and drag reduction. When the deep-stall angle α is larger than 20° (either positive or negative), relatively low F⁺ values around 0.25 were effective for lift recovery. When actuating at a deep-stall angle corresponding to F⁺ = 0.25, the surface pressure measurements showed that a near flat pressure distribution is formed on the suction side, and the PIV measurement showed that this near flat distribution is caused by the increase in backflow velocity near the surface of the airfoil. This backflow enhancement near the suction side surface leads to the reduction in pressure in separated flow, resulting in significant increases in the lift and drag coefficients. Thus, this simultaneous measurement of force, pressure, and PIV is capable of evaluating the multiple control modes underlying lift and drag control by ns-DBDPA. Graphical abstract: [Figure not available: see fulltext.].