The effect of stiffness and geometric parameters on the nonlinear aeroelastic performance of high aspect ratio wings

Abstract

The increase in wing aspect ratio is gaining interest among aircraft designers in conventional and joined-wing configurations due to the higher lift-to-drag ratios and longer ranges. However, current transport aircraft have relatively small aspect ratios due their increased structural stiffness. The more flexible the wing is more prone to higher deflections under the same operating condition, which may result in a geometrical nonlinear behavior. This nonlinear effect can lead to the occurrence of aeroelastic instabilities such as flutter sooner than in an equivalent stiffer wing. In this work, the effect of important stiffness (inertia ratio and torsional stiffness) and geometric (sweep and dihedral angles) design parameters on aeroelastic performance of a rectangular high aspect ratio wing model is assessed. The torsional stiffness was observed to present a higher influence on the flutter speed than the inertia ratio. Here, the decrease of the inertia ratio and the increase of the torsional stiffness results in higher flutter and divergence speeds. With respect to the geometric parameters, it was observed that neither the sweep angle nor the dihedral angle variations caused a substantial influence on the flutter speed, which is mainly supported by the resulting smaller variations in torsion and bending stiffness due to the geometric changes.

Non-linear aeroelastic response of high aspect-ratio wings in the frequency domain

“…With the goal of integrating the capabilities of analysing morphing solutions and novel configurations in a multidisciplinary design optimization environment, a computational framework was developed in the scope of the EU FP7 NOVEMOR project. To expand the potentialities of this tool in preliminary aircraft design, an aeroelastic module was devised with the possibilities of running linear and non-linear static aeroelastic analyses (3,35) . This framework was designed to be both modular and versatile.…”

“…The aeroelastic flutter boundary calculation is performed at the equilibrium state (similar to what was done in other works (3,13,16,33) ) using the p-k method and the updated stiffness and mass matrices obtained from the non-linear equilibrium. If a linear structural analysis is chosen instead in the aeroelastic module, the flutter speed calculation is performed using the undeformed stiffness and mass matrices.…”

“…For this work, an in-house non-linear aeroelastic framework (3,35) with the capability of analysing the aeroelastic behaviour of very flexible low-speed aircraft was used.…”

On the Design of Aeroelastically Scaled Models of High Aspect-Ratio Wings

“…An in-house nonlinear aeroelastic framework described in [33,34] was used in this work. This framework is capable of analyzing flexibility effects on high aspect-ratio wings in the time domain considering both constrained, i.e., simulating wind tunnel conditions, and unconstrained i.e., emulating free-flight conditions, models.…”

“…Despite the use of low-medium fidelity aerodynamic (3D panel method with viscous and compressibility corrections) and structural (3D condensed beam model based on wing-box mass and inertia calculations) models, their applicability to preliminary design is adequate since they capture the main physical phenomena and allow exploring the design space [35,36]. The aerodynamic, structural and aeroelastic models were benchmarked [33,34] with existing data available in the literature. Furthermore, the application of this framework to estimate the aeroelastic behavior of both full and reduced size models ensures comparability between these models.…”