FLUTTER AND TIME RESPONSE ANALYSES OF THREE DEGREE OF FREEDOM AIRFOILS IN TRANSONIC FLOW

CHIA-HSIN CHEN, Purdue University

Abstract

Flutter and time response analyses are performed for a NACA 64A006 conventional and a MBB A-3 supercritical airfoil, both oscillating with plunge, pitch, and aileron pitch degrees of freedom in transonic, small disturbance flow. The aerodynamic coefficients are calculated using the transonic code LTRAN2-NLR. The effects of various kinds of aeroelastic parameters on flutter speeds for the bending-torsion, bending-aileron, and torsion-aileron branches are studied. The flutter speeds associated with the bending-torsion branch are plotted against Mach number for different parameter values, and the transonic dip phenomenon is demonstrated. To study the flutter modes, the flutter speed, the amplitude ratio, and the phase difference are plotted against the mass ratio for both a two degrees of freedom and a three degrees of freedom case. Time response results are obtained for the NACA 64A006 and MBB A-3 airfoils at M = 0.85 and 0.765, respectively. Using the same set of parameter values, the flight speed used to obtain the neutrally stable responses are very close to the flutter speeds obtained in the flutter analysis. The principle of linear superposition of airloads is used in the flutter analysis but not in the response analysis.

Degree

Ph.D.

Subject Area

Aerospace materials

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