Gust enhancement using jet at the trailing edge of a pair of pitching foils

Abstract

A fluid dynamics numerical simulation is carried to study the gust characteristics produced downstream of a pair of sinusoidally pitching two-dimensional thin foils with a certain lateral spacing and placed in a freestream flow. The flow was simulated for Reynolds number (Re) = 1.6 × 105, the airfoil pitching angle = 6.9°, and a range of reduced frequencies (0.54 ≤ k ≤ 1.2). Between the two (undulating) wakes of the two foils, the flow is irrotational and unsteady that can be used to study gust response of, for example, micro-air vehicles (MAVS). The maximum gust velocity that can be generated by this technique is, however, limited to (5–7) % of the mean flow velocity. To enhance the gust intensity, a new method is proposed: introduction of a jet at the trailing edge of each pitching foil. Results show that the addition of the trailing jet enhances the gust intensity by 2–7 times for the Re, jet velocity, and the range of reduced frequencies considered. This technique provides a simple, economical, and controlled way to study gust response of MAVs and aircraft in wind tunnels.