Coupled aerodynamic and structural optimization of a subsonic-transport wing using surrogate model

Coupled aerodynamic and structural optimization is performed for the preliminary design of a high-subsonic transport-aircraft wing using surrogate models. The aerodynamic performance of wing/body combination in transonic flow is calculated with full-potential equation in conjunction with viscous correction method. Structural analysis is performed using finite-element method (FEM) to obtain stress and deform distribution. The span, taper ratio, sweep angle and linear twist angle are chosen as design variables that define the aerodynamic configuration of the wing. And another four representing thicknesses of spars and skin are selected as the design variables for structural discipline. After the aeroelastic analysis of the various candidate wings, the aerodynamic and structural performances are obtained such as the lift coefficient, the drag coefficient, and the deformation and equivalent stress of the wing. Based on these sample data, the approximation models for analyzing the aerodynamic and structural performances are established using surrogate models including quadratic response surface method (RSM), kriging model (KM) and radial-basis function (RBF) Network. The modeling accuracy is evaluated by numerical-error analysis. We aim to select the approximation models with best accuracy to replace the complicated and time-consuming analysis in optimization. It is found that KM and RSM has comparative high accuracy and both are more accurate than RBF. Multi-objective optimization for the supercritical wing is performed based on RSM, for maximizing lift-to-drag ratio and minimizing weight. And the optimization is constrained by lift, reference area, deform, equivalent stress. The performance of the optimal design is proven to be improved based on the initial design. And compared with the optimal design without considering aeroelastic effect, lift-to-drag ratio is increased by 5.77% and lift is increased by 19.55%. It is proven by practice that considering aeroelastic effect is necessary in priliminary design of aircraft when optimizing high-aspect-ratio wing.