Parallel vortex body interaction enabled by active flow control

An experimental study has been conducted to explore the flow physics of parallel vortex body interaction between two NACA 0012 airfoils in series. Experiments were carried out at a chord-based Reynolds number of 740,000. Active flow control in the form of nanosecond pulse driven dielectric barrier discharge plasma actuation, originating close to the leading edge, was used to produce vortex shedding from the upstream (disturbance) airfoil at various frequencies (0.038 ≤ F⁺ ≤ 0.762). These vortices were characterized before examining the downstream wake-airfoil interactions in detail. Time-resolved pressure and phase-locked PIV measurements were conducted on the downstream (target) airfoil for multiple angles of attack. For F⁺ ≤ 0.5, the target airfoil is subject to strong oscillations from the wake of the disturbance airfoil that lead to large fluctuations in lift and pitching moment. However, a further increase in F⁺ reattaches the flow over the disturbance airfoil and no major vortex body interactions are observed on the target. Governing parameters for this type of vortex body interaction are explored and differences between isolated and non-isolated encounters as well as the presence of a viscous response are examined.