Control of separation on a swept wing using fluidic oscillators

The performance of a flapped wing based on a NACA 0012 airfoil section and equipped with a linear array of fluidic oscillators was investigated experimentally to assess the significance of wing sweep and tip shape on the efficiency of this actuation technique. The semi-span wing was suspended from the wind tunnel ceiling through a six-component balance and could be rotated relative to the oncoming flow. Thus, its sweep could vary from 0° to ±45° while maintaining a constant aspect ratio of the wing. The experiments were carried out at a Reynolds number of approximately 500,000. The boundary layer was tripped in order to fix the location at which transition to turbulence occurs. The effects of incidence, flap deflection, and the level of the actuation were the independent parameters affecting the wing’s performance. In contrast to non-swept wings equipped with fluidic oscillators, the swept-back wing requires a substantially lower input level of actuation to improve the lift generated by the wing and alter its pitching moment provided the aggregate number of the actuators used was small. For this study, the number of active actuators did not exceed two. Under these conditions, the actuators acted as fluidic fences that re-orientated the flow by reducing its spanwise component. Since this is an interim report in an ongoing investigation, it will focus on issues that were not reported at the AIAA meeting in Atlanta. For example, a two-actuator pattern (the spacing between them was kept constant) was moved along the wingspan and the impact of their location on performance was analyzed with respect to the sweep angle.