Unsteady aerodynamics of a morphing tandem-wing unmanned aerial vehicle

The effects of unsteady aerodynamics for a tandem-wing unmanned aerial vehicle (UAV) prototype during the morphing stage have been investigated numerically at low Reynolds numbers (Re < 106). The morphing stage consists of two stages. The first stage involves the unfolding of the canards and wings from their initial position in which they were attached and aligned parallel to the UAV fuselage. The second stage involves the rotation of the unfolded canards and wings around the chord axis toward their final orientations. Lift and drag coefficients for the canard and wing vary significantly, particularly during the second morphing stage. Maximum deviation can be 2 to 14 times higher than the final steady state values. A significant increase in the hinge moment is also observed during the first morphing stage but the sign of the moment remains the same throughout. The unsteady aerodynamics, however, have larger effects during the second morphing stage, including the rapid change in the sign for the hinge moment, the corresponding magnitude also differs by (+) 57% and (-) 260% for the canard and wing, respectively. Attempts have been made to correlate these observations with the vortex interactions between the canard and wing during the morphing process.