Weight Indexing for Wing-Shape Multi-Objective Optimization

Abstract

A method for wing-shape optimization is presented, in which the wing outer shape is optimized not only for the best aerodynamic efficiency but also for the minimum structural weight. The so-called airfoil effective distance is used to capture the influence of the wing outer shape on the wing-box structural weight. The airfoil weight index is defined based on the airfoil effective distance. Increasing the airfoil weight index results in decreasing the structural weight. The weight indexing method is used for airfoil multi-objective optimization for minimizing the aerodynamic drag as well as maximizing the weight index. The Pareto front for the drag and weight is found, and the airfoils on the Pareto front are used as the basis airfoils for a three-dimensional wing-shape optimization. The same method is applied to optimize the outer shape of three-dimensional wings for two objective functions: minimizing the wing drag and minimizing the wing structural weight. A response surface methodology is used to reduce the computational costs of the wing-shape optimization. The influence of the material used in the wing-box structure on the wing optimum outer shape is also investigated. Three different composite layups together with a metal alloy are tested. The aircraft maximum takeoff weight and the aircraft direct operating cost are used as the design figures of merit to identify the best wings among the wings on the Pareto fronts. The results show that the optimum wing outer shape is significantly influenced by the material used in the wing-box structure.