Experimental Investigation of the Flow Control Algorithm Using Fluidic Oscillator Array on NACA 0018 Airfoil

This study parametrically investigates the effectiveness and efficiency of the active flow control technique on a NACA 0018 airfoil using a sweeping jet actuator (SWJ) array implemented at the airfoil's leading edge. Three parameters (i.e., the momentum coefficient, Cμ, injection angle β, and actuators’ spanwise spacing, Δz/D) were systematically varied with an interchangeable leading-edge section design. Experiments were conducted in a closed-loop wind tunnel at a fixed Reynolds number of 1.2×10^5, combining force measurements using a force sensor and velocity field measurements through planar particle image velocimetry (PIV) on various streamwise planes spanning. The measurement planes were spanned from the actuator exit to the mid-spacing location between adjacent actuators. Results show that both the maximum lift coefficient and the critical angle of attack increase logarithmically with the increase of Cμ. The injection angle β is found strongly affect post-stall behavior: the case of β = 20 deg and 80 deg produced more gradual post-stall lift decrease, while β = 50 deg yielded a decay efficiency at the same jet injection conditions. PIV measurements revealed that AFC reduced trailing-edge separation in the pre-stall regime and suppressed or displaced leading-edge separation in the post-stall regime, with the extent of control depending on both β and Δz/D. The velocity profiles confirmed a notable reduction of the separation region and near-wall velocity augmentation for higher Cμ. The different injection angles will also result in different altered boundary-layer profiles.