Impact of Low-Order Modeling on Aeroelastic Predictions for Very Flexible Wings

Abstract

This paper investigates the ability of low-order structural and aerodynamic models to predict geometrically nonlinear aeroelastic behaviors associated with large wing deflections. The study considers the Pazy wing, a very flexible wing developed at the Technion—Israel Institute of Technology for geometrically nonlinear aeroelastic benchmark studies in low-speed flow. The low-order model of the wing consists of a geometrically nonlinear beam with properties derived from a built-up finite element model coupled with potential flow strip theory with tip loss correction to account for three-dimensional aerodynamic effects. The beam structural model predicts the wing modal characteristics and static response as accurately as the parent built-up finite element model while using much fewer degrees of freedom and showing higher numerical stability. The low-order aeroelastic model predicts the wing static response for various flow conditions with accuracy comparable to a higher-order model based on the vortex-lattice method. Flutter onset points differ from reference solutions by up to 8% with lower differences in the presence of larger wing deflections. These differences arise from approximating three-dimensional unsteady aerodynamic effects using tip loss corrections, while reducing the built-up structure to a beam impacts the flutter results slightly. The insights from this study will inform appropriate-fidelity modeling choices for aeroelastic analysis of very flexible wings in the design and optimization of energy-efficient, high-aspect-ratio-wing aircraft.