Accession Number : ADA320433

Title :   A Formulation of Nonlinear Limit Cycle Oscillation Problems in Aircraft Flutter.

Descriptive Note : Final rept. 15 Sep 92-14 Jul 93

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE TECHNOLOGY LAB FOR ADVANCED COMPOSITES

Personal Author(s) : Chen, Warren C. ; Dugundji, John

PDF Url : ADA320433

Report Date : 30 SEP 1993

Pagination or Media Count : 150

Abstract : A simple nonlinear aeroelastic flutter analysis method was developed. The aerodynamic forces were modeled by using the ONERA aerodynamic formulation. The ONERA aerodynamic model, a semi-empirical, unsteady, nonlinear model, was reformulated into a harmonic balance form. Fining of the ONERA aerodynamic formulation was required to incorporate the model into the analysis. The model was fitted to experimental aerodynamic stall flutter characteristics of NACA 0012 airfoil obtained by McAlister, Pucci, McCroskey and Carr. A linear flutter analysis was performed using the U-g method as a basis for comparison with the stall flutter formulation. Nonlinear flutter calculations were done by applying the harmonic balance method to the flutter equations and solving by the Newton-Raphson technique. The results yielded nonlinear limit cycle oscillations which exhibited the expected trends. As the root angle of attack increased, the flutter speed decreased, while the flutter frequency increased toward the torsional natural frequency. The analytic results compared favorably with previous experimental works by Dunn. The current nonlinear analysis procedure seems an effective technique for analyzing stall flutter phenomena.

Descriptors :   *AEROELASTICITY, *FLUTTER, *COMPOSITE WINGS, COMPUTER PROGRAMS, HARMONICS, ANGLE OF ATTACK, RESONANT FREQUENCY, STALLING, MATHEMATICAL ANALYSIS, AERODYNAMIC FORCES, BALANCE, NONLINEAR ANALYSIS, UNSTEADY FLOW, OSCILLATION, TORSION.

Subject Categories : Aerodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE