Accession Number : AD0676682

Title :   NONLINEAR OSCILLATIONS OF ELASTIC PANELS IN A SUPERSONIC NONVISCOUS AIRSTREAM.

Descriptive Note : Scientific interim rept.,

Corporate Author : STANFORD UNIV CALIF DEPT OF AERONAUTICS AND ASTRONAUTICS

Personal Author(s) : Eastep,Franklin E.

Report Date : AUG 1968

Pagination or Media Count : 128

Abstract : A variational analysis is presented for the problem of a panel under the influence of both random excitation (turbulent boundary layer) and aerodynamic loading. Geometric nonlinear effects in the panel are taken into account, and a (Rayleigh-Ritz) modal approximation is used to represent the spatial variation of the displacements. The supercritical (beyond linear flutter boundaries) limit-cycle amplitude and frequency are determined by assuming a Fourier-series representation for the modal amplitudes, thereby reducing the problem to solving a set of nonlinear algebraic equations. The aerodynamic loads resulting from the panel deformation are approximated by linear piston theory. Random excitation in the form of a pressure with known spatial and temporal correlations is then introduced. The forced response is calculated with the aid of Fourier-transform techniques and a method of equivalent linearization at flow conditions below and above the stability boundary for classical panel flutter. The effect of random excitation on the supercritical response is reduced to a study of coupled nonhomogeneous Mathieu equations. The solution of these equations is determined approximately using the digital computer. The determination of the amplitude of response and the frequency of oscillation provides the necessary information for a fatigue analysis. (Author)

Descriptors :   (*AIRFRAMES, PANELS), (*PANELS, FLUTTER), ELASTIC SHELLS, SUPERSONIC FLOW, OSCILLATION, ANALYSIS OF VARIANCE, TURBULENT BOUNDARY LAYER, AERODYNAMIC LOADING, NONLINEAR SYSTEMS, NUMERICAL ANALYSIS, EQUATIONS OF MOTION, DIFFERENTIAL EQUATIONS, CYLINDRICAL BODIES, METAL PLATES, RESPONSE, THESES

Subject Categories : Structural Engineering and Building Technology
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE