Increasing the Lift-Drag Ratio of an Unmanned Aerial Vehicle Using Local Twist

Recently published works predict that any planform shape may be optimized with twist to reduce the induced drag to an optimum value. When the twist is applied along the span of the airplane, the lift-drag ratio is lower than that with no twist. This can be corrected if twist is applied only in a specific portion of the span. The objective of this paper is to demonstrate that the local twist increases the lift-drag ratio using two different inviscid computational fluid dynamics codes and to describe the method employed to obtain the twist start line to increase the lift-drag ratio. The method was applied to an unmanned aerial vehicle designed for the early detection of oil leakages in the extraction areas, and a variation of 8 cm in the wing tip was obtained. The results show that the lift-drag ratio of the twisted wing is higher than that with no twist in conditions close to cruise flight. The lift-drag ratio increased 2.89 and 0.31%, estimated by Multhopp's method and by the vortex-lattice method, respectively. The results demonstrate that the local twist may increase the lift-drag ratio when it is applied in the way explained in the present paper.