Flutter analysis of a two-dimensional airfoil containing structural hysteresis nonlinearities

Aeroelastic flutter is a dangerous phenomenon where aerodynamics interact with the structure of an aeronautical component to produce potentially damaging oscillations. Small concentrated structural nonlinearities can have significant effects on the flutter behaviour and can, in particular, cause large-amplitude oscillations at lower airspeeds than for linear systems.;This thesis documents an investigation of one particular type of nonlinearity, hysteresis. The effects of introducing hysteresis into an otherwise linear aeroelastic system are determined. This work was a continuation of previous work that examined the effects of bilinear and cubic type nonlinearities in a dynamic system consisting of a two-dimensional airfoil having two degrees of freedom. This thesis first outlines a method of characterizing the response of the system through the use of a finite difference formulation to produce a time marching simulation that traces the response of the system through time. A second solution method outlined is a semi-analytical method using a Describing Function technique to approximate the amplitude of the response of the system based on the nonlinearity present.;Results are presented in the form of "maps" that indicate configurations where Limit Cycle Oscillations (LCO) are induced, and in the form of amplitude versus airspeed plots for the LCO cases. The simulation and describing function methods were found to compare with reasonably good accuracy. It was found that the Describing Function solution tends to become less accurate as the assumptions of sinusoidal motion break down.