Characterization of the Wake of a Gust Generator for Unsteady Aerodynamics Applications

Gusts are common incidents in nature which can rapidly change the aerodynamic forces experienced by the birds, insects, and micro aerial vehicles (MAVs). Despite the great progress in their design and control, these machines are tremendously troubled while flying in turbulent environments due to rapid changes in forces that result in large safety and stability factors. An experimental investigation was conducted to characterize the gust environment generated by a cascade of sinusoidally oscillating vanes in a closed-circuit water channel. Particle Image Velocimetry (PIV) was employed to quantitatively study the wake of this gust generator at different upstream flow speeds, oscillating frequencies, and amplitudes. The vertical components of velocity and turbulence intensity were shown to be consistent for the range of measurement points chosen. The peak vertical velocity component downstream of the vanes was shown to be proportional to the maximum vane angle of attack but largely independent of reduced frequency. This gust generator is used to understand the effect of unsteady wake on the flow measurements of flapping wings which may eventually lead to more efficient or better-performing MAVs.