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A parametric study of the interaction between dynamic stall and a zero-net mass flux synthetic jet installed on a wing was investigated by identifying the dominant frequencies in the resulting flow field using spectral analysis. The instantaneous pressure distribution around an NACA 0020 wing was recorded by performing static and dynamic experiments using an open jet subsonic wind tunnel located at the aerodynamics laboratory of the University of New South Wales. The results obtained provided valuable insight into the interaction process. The oscillation frequency and its harmonics were identified in baseline dynamic experiments, as well as the jet frequency and offset frequencies with synthetic jet actuation. The offset frequencies, similar to beat frequencies, were found to be a dynamic effect and represented the complex and nonlinear interaction between dynamic stall and the synthetic jet. The study suggests that low amplitude synthetic jet actuation would be an effective method in enhancing the overall aerodynamic efficiency of the wing. This confirmed the viability of utilizing synthetic jets in dynamic stall control.

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Vorticity creation and its evolution play an important role in the formation of large dynamic stall vortices which cause large excursions in lift, drag and pitching moment on rapidly pitching and oscillating airfoils. While synthetic jets have shown potential in controlling dynamic stall vortices by sustaining lift increases without corresponding drag and pitching moment, their effect on the vorticity creation remains unknown. To address this, high fidelity computational fluid dynamics simulations were conducted to investigate how synthetic jet frequency and orientation alter the dynamic stall leading-edge boundary vorticity flux. Changes in baseline boundary vorticity flux were related to corresponding flow fields to delineate the role of synthetic jets in vorticity creation. Slot orientation was found to play a greater role in altering the amount of vorticity diffused into the flow than actuation frequency. Dynamic stall vortex sizes were found to be directly proportional to the vorticity diffused from the leading-edge and could therefore be effectively manipulated using synthetic jets. The study provides a better understanding of the dynamic stall vorticity creation process and its control using synthetic jets. Nomenclature ‫ܣ‬= synthetic jet amplitude, ‫ݏ݉‬ ିଵ = acceleration ‫ܥ‬ ఓ = synthetic jet momentum coefficient, ሺ݀ ܿ ⁄ ሻ൫ܷ ,௫ ܷ ஶ ⁄ ൯ ଶ ܿ = chord length ݀ = slot width = body force ݂ = airfoil oscillation frequency, ‫ݖܪ‬ ݂ = jet actuation frequency, ‫ݖܪ‬ ݂ ା = non-dimensional actuation frequency, ݂ ‫ݔ‬ ்ா ܷ ஶ ⁄ = unit normal vector pointing out of the flow ܲ = pressure ܴ݁ = chord Reynolds Number, ߩܷ ஶ ܿ ߤ ⁄ ‫ݏ‬ = distance along surface ‫ݐ‬ = time ܷ ,௫ = maximum jet velocity during blowing phase, ‫ݏ݉‬ ିଵ ܷ ஶ = freestream velocity ‫ݔ‬ ்ா = distance from synthetic jet to trailing-edge ߛ = slot orientation ߢ = reduced airfoil oscillation frequency, ߱ܿ 2ܷ ஶ ⁄ ߤ = dynamic viscosity ߩ = density = boundary vorticity flux, ‫ݏ݉‬ ିଶ ࣓ = vorticity ߱ = airfoil angular frequency, 2ߨ݂ ߱ = jet angular frequency, 2ߨ݂