Coupled adjoint aerostructural wing optimization using quasi-three-dimensional aerodynamic analysis

Abstract

This paper presents a method for wing aerostruc-tural analysis and optimization, which needs much lower computational costs, while computes the wing drag and structural deformation with a level of accuracy comparable to the higher fidelity CFD and FEM tools. A quasi-three-dimensional aerodynamic solver is developed and connected to a finite beam element model for wing aerostruc-tural optimization. In a quasi-three-dimensional approach an inviscid incompressible vortex lattice method is coupled with a viscous compressible airfoil analysis code for drag prediction of a three dimensional wing. The accuracy of the proposed method for wing drag prediction is validated by comparing its results with the results of a higher fidelity CFD analysis. The wing structural deformation as well as the stress distribution in the wingbox structure is computed using a finite beam element model. The Newton method is used to solve the coupled system. The sensitivities of the outputs, for example the wing drag, with respect to the inputs, for example the wing geometry, is computed by a Ali Elham a.elham@tudelft.nl Michel J. L. van Tooren combined use of the coupled adjoint method, automatic differentiation and the chain rule of differentiation. A gradient based optimization is performed using the proposed tool for minimizing the fuel weight of an A320 class aircraft. The optimization resulted in more than 10 % reduction in the aircraft fuel weight by optimizing the wing planform and airfoils shape as well as the wing internal structure.

Concurrent wing and high-lift system aerostructural optimization

“…The present research expands the methodtool developed by Elham and van Tooren (2016a) for coupled-adjoint aerostructural analysis and optimization of lifting surfaces to include the analysis and optimization of HLD. This tool employs a Q3D method to compute the aerodynamic characteristics of a wing.…”

“…For a complete description of this coupled-adjoint aerostructural analysis and optimization method and derivation of the coupled-adjoint method, the reader is referred to Elham and van Tooren (2016a).…”

“…To analyze the airfoil using the panel method code the effective angle of attack and the effective Mach number are required. These values are obtained from the global angle of attack and free stream Mach number by adjusting for sweep effects and downwash (see Elham and van Tooren (2016a) for more details).…”

“…While the aerostructural tool developed by Elham and Van Tooren has been validated for wing drag and wing deformation (Elham and van Tooren 2016a), the enhanced method needs to be validated for maximum wing lift coefficient prediction and computation of wing lift over drag ratios in high-lift conditions. Finally, the sensitivities are verified through Finite Differencing (FD).…”

“…Examples of using the Q3D method for aerodynamic analysis was presented by van Dam (2002), Elham (2015) and Mariens et al (2014). Elham and Van Tooren developed a coupled-adjoint aerostructural analysis and optimization tool by coupling a Q3D method to a FEM (Elham and van Tooren 2016a). This tool has been validated for drag prediction and twist deformation.…”