A Study of Wind Shear Influences on the Aerodynamic Performances of a UAV Airfoil

In order to study the flight strategies of birds in shear wind and realize the long-range flight of an unmanned aerial vehicle (UAV), the aerodynamic performances of a UAV’s airfoil under different shear wind are studied using numerical methods. The results are calculated using the RANS method in shear wind with a linear and logarithmic distribution of velocity. The results show that the slope of the lift curve, the maximum lift coefficient and the stall angle decrease when the velocity gradient is positive or increasing, conversely, they increase at a negative gradient compared to gradient-free wind fields. A positive gradient of wind significantly increased the maximum lift-drag ratio and the effective angle of attack. Compared with linear distributed shear wind with the same velocity at both the lowest and highest points of the flow field, logarithmic distribution decreases the slope of the lift curve, the maximum lift coefficient and the maximum lift-drag ratio and the effective angle of attack. Therefore, a shear wind with a positive gradient is beneficial to the increase of lift-drag ratio and more conducive to cruise flight, and a negative gradient is beneficial for increased lift and more conducive to take-off and landing of UAVs. The velocity distributions influence the aerodynamic performances of the airfoil which is related to the speed and gradient distribution of shear wind.