University of Washington, Seattle, WA 98195, USANASA Ames Research Center, Moffett Field, CA, 94035, USAUniversity of Washington, Seattle, WA 98195, USAUniversity of Washington, Seattle, WA 98195, USA
Gustavo E. C. Fujiwara;Nhan T. Nguyen;Eli Livne;Michael B. Bragg
Morphing wing technology offers the potential to improve the fuel efficiency of commercial transport aircraft by allowing wings to continuously adapt to changing flight conditions. The Variable Camber Continuous Trailing Edge Flap is a novel morphing wing mechanism that can be used to reduce aerodynamic drag and critical loads acting on the wing structure by changing the wing shape in flight. This work is motivated by the need to evaluate performance benefits from such wing-morphing system, accounting for the added weight of the required additional flap hardware and flap actuatorsm, when used on a long-range wide-body transonic aircraft configuration known as the undeformed Common Research Model (uCRM). The aerostructural mathematical models used for system optimization include, in aerodynamics, a 3D full-potential flow equations solver coupled with an integral boundary layer model, and in the structural area a 3D equivalent beam finite element model especially tailored to capture key structural behavior. Flap deflections of the given-planform wing and the wing-box cross sectional structural dimensions are parametrized and used as design variables. Aerostructural sensitivities are computed using a coupled-adjoint method, and an aggregation function can, optionaaly, be used to reduce the number of structural constraints. The goal is to investigate three scenarios: pure aerodynamic shape optimization of the flap deflections for a rigid wing with no structural deflection, aerodynamic shape optimization of the flap deflections considering the aeroelastic deflection of a flexible wing of given wing-box structure, and an aerostructural optimization of both the flap deflections and wing-box structure cross-sectional dimensions simultaneously. Preliminary results for the pure aerodynamic shape optimizations of the flaps' motions show that the morphing trailing-edge system studied here can achieve fuel-burn reduction of 3.2% on the rigid wing, and 2.7% on the flexible wing over the nominal 7725 nm-range mission. Optimizing both the aerodynamic shape of the flaps and the wing-box structure altogether yielded a fuel burn reduction of 4.7% through a combination of aerodynamic drag reduction at cruise and structural load alleviation at a critical maneuver condition, resulting in a more aerodynamically-efficient cruise configuration with a lighter wing structure.