CFD corrected static aeroelastic stiffness optimization of a passenger aircraft wing

Kurzfassung

This paper presents the application of a static aeroelastic stiffness optimization process to a passengertype aircraft wing. In order to improve the aeroelastic load calculation, which is typically based on a doublet lattice panel method, a computational fluid dynamics (CFD) correction method is applied. The wing geometry and the corresponding shell finite element model of the load carrying structure are generated with ModGen, a parametric model generator used in combination with the finite element code Nastran. Design variables in the gradient based optimization process are the membrane and bending stiffness matrices A and D. Shell elements are grouped in so-called design fields in wing skins and spars, each of which features a unique set of stiffness matrices. The responses to be considered in the optimization consist of the classical structural quantities mass, strain and buckling, as well as the aeroelastic constraints aileron effectiveness, divergence and twist. The optimization is based on the minimization of an approximated sub-problem. To this end, linear and reciprocal approximations of the responses to be considered are set up, relying on the response sensitivities evaluated with Nastran. After a successful minimization of the local problem, the new set of design variables serves as an input for the generation of a new local approximation problem. The loop is repeated till convergence of the optimization objective. Results are presented for various combinations of responses and laminate types. While mass is always the optimization objective, optimizations with and without aileron effectiveness, as well as for balanced and unbalanced laminates are discussed. In order to assess the influence of the CFD correction on the optimization results, each optimization set is performed with and without correction.