Numerical analysis of a biomimetic UAV with variable length grids wingtips
Rafael Bardera, Ángel Antonio Rodríguez-Sevillano, Estela B. Barderas, Juan Carlos Matías-García
Abstract
Birds can reduce the induced drag using an elongation of the wings called primary feathers. In this paper, a numerical analysis of a biomimetic Unmanned Aerial Vehicle (UAV) that imitates that elongation at its wing tips is presented. Specifically, the UAV has a rectangular wing and three grids at the tip that changes the lift distribution over the wing. By using Computational Fluid Dynamics (CFD) the effect of the grids span has been compared for the UAV without grids and for 1/3, 2/3, and fully extended grids. Grids with a variable size along the chord are also tested. The aerodynamic performance (lift, drag, and efficiency), and the rolling capabilities have been obtained under different flight conditions. The results have demonstrated that an increase of grids span translates into a 15–20% increase in aerodynamic efficiency of the UAV during cruise and climb phases of the flight. The grids also provide the ability for rolling under positives angles of attack.