The Numerical Prediction and Optimization Design of Natural Laminar Airfoil for UAV

Abstract

The enhancement of the lift to drag ratio of the wing is the goal pursued for the aerodynamic design of the Unmanned Aerial Vehicle (UAV). The natural laminar airfoil technology is an efficient way to reduce friction drag. This work focuses on the Computational Fluid Dynamics (CFD) method in predicting the transition process and the optimization design method for the laminar airfoil. A three-equation turbulence model $$k-\overline{{v }^{2}}-\omega $$ is adopted to predict the transition performance, and the effectiveness of the model is verified by the S809 and NLF0416 laminar airfoils. The design concept of these natural flow laminar airfoils is compared. In the optimization design process of the natural laminar wing of UAV. A wing platform with a high aspect ratio is used under low Reynolds number flight conditions. Class Shape Transformation (CST) method is used as a geometry parameterization method. The Genetic Algorithm is adopted as the optimizer. Results show that the optimized UAV wing has a laminar region up to 45% chordwise length on the wing's upper surface, and 65% chordwise length on the lower surface, which promotes the lift to drag ratio of the whole UAV up to 25.