Dynamic Response of Highly Flexible Flying Wings

Abstract

This paper presents a method to model the coupled nonlinear flight dynamics and aeroelasticity of highly flexible flying wings, as well as analyze their nonlinear characteristics. A low-order, nonlinear, strain-based finite element framework is used, which is capable of assessing the fundamental impact of structural nonlinear effects in a computationally effective formulation target for preliminary vehicle design and control synthesis. The crosssectional stiffness and inertia properties of the wings are calculated along the wing span, and then incorporated into the 1-D nonlinear beam model. A proposed model for the effects in the torsional stiffness of skin wrinkling due to large bending curvature of the wing is also presented. Finite-state unsteady subsonic aerodynamic loads are incorporated to complete the aeroelastic representation of a flying wing. In studying flying wing dynamic response, a spatially-distributed discrete gust model is introduced and its impact on the time-domain solutions is investigated.

Optimum Wing Shape of Highly Flexible Morphing Aircraft for Improved Flight Performance

“…Solutions of the coupled aeroelasticity and flight dynamics using the strain-based geometrically nonlinear beam formulation have been discussed by Su and Cesnik [14,15,18]. An introduction of the strain-based aeroelastic equations is presented here, followed by the modal-based optimization formulation for searching the optimum wing geometries under different flight conditions.…”

“…[14,15]. The generalized force vector is (6) where N, B F , and B M are the influence matrices for the gravity force, distributed forces, and distributed moments, respectively, which come from the numerical integration.…”

“…The structural dynamic and aeroelastic characteristics of the aircraft may change significantly due to the large deflections of their flexible wings. In addition, highly flexible aircraft usually see the coupling between the low-frequency elastic modes of their slender wings and the rigid-body motions of the complete aircraft [11][12][13][14][15]. Therefore, the coupled effects between the large deflection due to the wing flexibility and the aeroelastic/flight dynamic characteristics of the complete aircraft must be properly accounted for in a nonlinear aeroelastic solution.…”

“…Without modeling the builtup wing structures, a homogenized set of aircraft properties will be used as inputs to a strainbased nonlinear aeroelastic formulation for the complete aircraft modeling. This formulation has been successfully used to design and analyze different highly flexible aircraft configurations [14,15,17]. To find the optimum wing shape among the complex space of the wing deformations, a modal-based optimization scheme will be developed, which satisfies the required trimming condition of the aircraft.…”

Integrated Flight Dynamics and Aeroelasticity of Flexible Aircraft with Application to Swept Flying Wings

“…This has forced engineers to develop multi-disciplinary computational tools for early-stage and control system design that can predict the interaction of aircraft elastic response, rigid-body motion, and aerodynamic forcing. 1,2,3,4,5,6 In addition to this, several flight test programs 7,8 have been developed recently that specifically target the phenomenon of aeroelastic/rigid-body coupling with the intention of developing active aeroelastic control systems for stability augmentation and disturbance rejection. Most saliently, the intended handover of the Lockheed-developed X-56 Multi-Utility Technology Testbed (MUTT) to NASA has created a focal point for public domain research into flexible aircraft flight dynamics (FAFD) and control.…”