Geometrically nonlinear high-fidelity aerostructural optimization for highly flexible wings.

Area of Science:

• Aerospace Engineering
• Computational Mechanics
• Optimization Theory

Background:

• Multidisciplinary Design Optimization (MDO) advances enable simultaneous aerodynamic and structural wing design using high-fidelity models.
• Current MDO methods accurately trade off drag and mass but struggle with geometrically nonlinear behavior in high-aspect-ratio wings.
• Linear structural analysis is insufficient for modeling the extreme flexibility and nonlinearities of next-generation aircraft wings.

Purpose of the Study:

• To demonstrate the first simultaneous optimization of wing aerodynamic shape and structural sizing using high-fidelity geometrically nonlinear models.
• To develop and implement computational tools for nonlinear structural analysis and aeroelastic coupling.
• To investigate the impact of geometric nonlinearity on the design and performance of highly flexible aircraft wings.

Main Methods:

• Implementation of a novel geometrically nonlinear shell element, an efficient nonlinear solver, and a constitutive model for stiffened shells.
• Coupling nonlinear structural analysis with Computational Fluid Dynamics (CFD) via a geometrically nonlinear transfer scheme.
• Optimization of a single-aisle commercial transport aircraft wing with 547 design variables and 1277 constraints.

Main Results:

• Optimized designs exhibit extreme flexibility (aspect ratio > 19, deflections > 30% semispan).
• Geometric nonlinearity had minimal impact on aerodynamic performance, planform, and overall aircraft mass.
• The Brazier effect, a nonlinear phenomenon, introduces significant internal loads missed by linear analysis, necessitating nonlinear methods for feasible designs.

Conclusions:

• The developed framework provides the computational foundation for designing next-generation high-aspect-ratio wings.
• Exploiting extreme wing flexibility through geometrically nonlinear analysis is key to designing more efficient aircraft.
• This research enables the pursuit of innovative wing designs by treating extreme flexibility as an opportunity, not a constraint.