21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-4.9.2

THEORETICAL STUDY OF TRANSONIC FLUTTER/BUZZ IN THE FREQUENCY AND TIME DOMAIN

Kouzmina S., Mosounov V., Ishmuratov F.
TsAGI, Russia

Keywords: transonic, flutter, buzz, frequency, time domain

The iterative method for transonic flutter calculation is developed. The problem of unsteady flow near elastic deforming wings at transonic Mach numbers is solved using Godunov finite-difference method of Euler equations integration. As initial approximation of frequency and deformation shape the result of flutter linear problem or experimental data are applied. The flow near the wing vibrating with· specified frequency and mode is analyzed by nonlinear transonic theory. Calculated pressure difference coefficients are used to obtain aerodynamic matrices through harmonic linearization procedure. Linear flutter equations with these matrices are solved in frequency domain. The process is then repeated up to flutter frequency convergence. Proposed method is illustrated by some flutter characteristic calculations for several aeroelastic structures: standard AGARD wing 445;6, fin with rudder, heavy transport aircraft. Various parameters influence on the transonic flutter is investigated. The controllable equations of motion of elastic aircraft are obtained taking into account nonlinear unsteady aerodynamic loads in the transonic flow. The method is proposed and developed to solve time domain equations. The comparative results of structure aeroelastic behavior are presented for linear, harmonically linearized and nonlinear transonic cases.

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