Flow control for aero-optics application

The mitigation of aero-optical aberrations in the wake of a surface-mounted turret comprised of a hemisphere mounted on a matching cylindrical support is investigated in wind tunnel experiments. The effects of hybrid (passive/active) flow control on the aero-optical and aerodynamic characteristics of the flow over a conformal optical aperture embedded in the hemispherical cap are investigated at M = 0.3 and Re _D = 4.46 × 10⁶. Direct optical diagnostics of 2D wavefronts over the aperture is performed using a high-speed Shack-Hartmann wavefront sensor for a range of aperture orientations on and off the streamwise center plane. Aerodynamic flow diagnostics includes arrays of static and dynamic pressure ports on the turret and the ground plane that help characterize flow separation and the wake topology. The global flow is passively controlled by a forward-facing partition plate that increases the flow receptivity to and the effectiveness of arrays of high-frequency fluidic oscillating jets that are placed upstream of the aperture. It is shown that the hybrid flow control yields significant improvements in the aero-optical characteristics of the flow over the aperture that exceeds the individual effects of passive and active control.