Non-Linear Flutter

Author: Fleming, Edward Richard

Year: 1960

Degree: Dissertation (Ph.D.)

Advisors: Fung, Yuan-cheng; Caughey, Thomas Kirk

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/CSNK-SA02

Abstract

The problem of two degree of freedom flutter in the presence of structural non-linearities is investigated. The specific problem chosen for investigation is that of bending-torsion flutter of a two-dimensional airfoil in a supersonic flow. The Kryloff-Bogoliuboff assumption of nearly sinusoidal response with slowly varying amplitude and phase is made and aerodynamic piston theory is used throughout the analysis.

Formulas for flutter limit cycles are developed in terms of general structural non-linearities. Necessary and sufficient conditions are developed for the existence of stable flutter limit cycles in the case of an airfoil with torsional stiffness. Several numerical examples of this case are given including a case which exhibits flutter for large disturbances but is stable at all airspeeds for small disturbances.

An analog computer investigation of flutter dependence on initial conditions is given.

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