Non-linear numerical simulation of a typical wing section with self-excited oscillations

Abstract

The response of flexible structures to aerodynamic loads is generally of non-linear nature. The characteristics of the aeroelastic behavior depend on the properties of structural-and-aerodynamic subsystems, and
also depend on the way in which these two subsystems are combined. The nonlinear response of a wing section
with two degrees of freedom has been widely studied. The importance of aeroelastic analysis relies on its ability
to predict the response of some critical aircraft components. For example, stiffness loss in the control surfaces
causes unacceptable vibration levels in the aircraft structure. These vibrations must be avoided because the transition between undesirable vibrations and flutter is generally diffuse. It is well known, that damage to the control surface caused by flutter may lead to the loss of the aircraft. In this paper we study numerically the dynamics of a nonlinear aeroelastic system with cubic-nonlinear and freeplay in the torsion stiffness of the wing section. This reduced order model uses the well-known typical-section hypothesis. The aerodynamic loads are obtained through a nonlinear bidimensional unsteady vortex lattice method. The integration of the governing equations of the coupled aeroelastic system is carried out numerically, simultaneously and interactively in the time
domain. Using the proposed model we can determine how a change in torsion stiffness influences the amplitude
and frequency of self-excited vibrations, the flutter speed of the aeroelastic system, and the occurrence of limit
cycles. Results from the numerical simulations show a significant correlation with those reported by other authors, in addition, the mathematical model presented here proved to be more efficient and accurate than other
models, particularly in highly nonlinear cases.