Nonlinear Flexibility Effects on Flight Dynamics of High-Aspect-Ratio Wings

2026-03-20

AI Summary

This study addresses the significant influence of geometric nonlinearity and structural deformation on the trim state, flutter boundary, and gust response of high-aspect-ratio flexible wings in flight. The authors develop a strongly coupled aeroelastic–flight dynamics framework that integrates a geometrically exact beam model, unsteady two-dimensional strip theory, and quaternion-based rigid-body equations of motion, enabling a unified single-step simulation of structural, aerodynamic, and flight dynamic interactions. For the first time, they systematically quantify how nonlinear static deflections—spanning from nearly rigid to ultra-flexible configurations—affect the effective dihedral angle, trim angle of attack, and long-period mode stability, revealing a pronounced reduction in flutter speed under pre-stressed conditions. Simulation results show excellent agreement with benchmark data in static deflection, natural frequencies, and flutter velocity, thereby delineating the validity limits of linear analysis and providing critical quantitative insights for the design of ultra-flexible aircraft.

Technology Category

• Application Domains: Mobility, Driving & Flight
• Intelligent Robots: State Estimation
• Cognitive Modeling & Cognitive Systems: Simulating Human Behavior

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• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
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Abstract

This paper investigates the effects of geometric nonlinearity and structural flexibility on the flight dynamics of high-aspect-ratio wings representative of high-altitude long endurance aircraft configurations. A coupled aeroelastic flight dynamic framework is developed, combining a geometrically exact beam formulation for the structure, unsteady two-dimensional strip theory for the aerodynamics, and quaternion-based rigid-body equations for the flight dynamics. The three subsystems are monolithically coupled through consistent load and motion transfer at each time step. A systematic parametric study is conducted by varying the wing stiffness across several orders of magnitude, spanning from nearly rigid to very flexible configurations. The study reveals that increasing flexibility fundamentally alters trim conditions, flutter boundaries, and dynamic gust response. In particular, large static deformations create an effective dihedral that modifies the lift direction and necessitates higher trim angles of attack. The phugoid mode is shown to destabilise at high flexibility levels, consistent with findings in the literature. Flutter speed degradation is quantified as a function of the stiffness parameter, showing significant reductions for very flexible configurations when the pre-stressed equilibrium is correctly accounted for. The framework is validated against published aircraft benchmarks, demonstrating good agreement in natural frequencies, flutter speeds, and nonlinear static deflections. Results provide quantitative guidance on when linear analysis is acceptable and when fully coupled nonlinear tools become essential.

Problem

• high-aspect-ratio wings
• geometric nonlinearity
• structural flexibility
• flight dynamics
• aeroelasticity

Innovation

• geometric nonlinearity
• aeroelastic coupling
• high-aspect-ratio wings
• monolithic integration
• flutter analysis