Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PANEL FLUTTER”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Orthotropic panel flutter at arbitrary yaw angles - Experiment and correlation with theory.

Experimental flutter boundaries were obtained for yaw angles between 15 and 90 deg at Mach numbers 2 and 1.6 for panels mounted on a remotely controlled turntable. Good definition of the flutter boundaries was obtained by rotating the panels into and out of flutter. Two types of specimens were tested: a single-sheet corrugated panel having a length-to-width ratio of 5 on clamped supports, and several square doubly-corrugated panels on various flexible supports. Calculated flutter speeds based on quasi-steady aerodynamics are compared to experimental data.

Shyprykevich, P.↗
NASA NTRS1972

The effect of hypersonic nonlinear aerodynamic loading on panel flutter.

The system considered is a two-dimensional isotropic panel, or plate-column, on hinged supports, with one end spring restrained in the plane of the panel. Panel geometric nonlinearities and piston-theory aerodynamic nonlinearities are included. Results from an earlier preliminary study indicate that only two second-order nonlinear aerodynamic terms are important. The nonlinear aerodynamic terms introduce the possibility of an amplitude-sensitive instability, where the panel is unstable to disturbances of a certain magnitude but stable for smaller ones. This type of instability is examined for various panel in-plane loads and initial conditions, with other parameters having values representative of current practice. A single new interaction parameter, representing the importance of the nonlinear aerodynamic terms in comparison with the panel geometric nonlinear terms, is introduced. A parameter survey is presented, involving this parameter and the static pressure difference across the panel. Finally, the practical impact of this type of instability is discussed.

Mcintosh, S. C., Jr.↗
NASA NTRS1991

Effect of temperature on nonlinear two-dimensional panel flutter using finite elements

A finite element formulation and solution procedures is presented for limit-cycle motions of 2D panels subjected simultaneously to thermal and aerodynamic loads. The thermal load is described by a steady-state temperature distribution and the quasi-steady first-order piston theory is used for aerodynamic pressure. The von Karman nonlinear strain-displacement relationship is used for the large panel deflections. Three temperature distributions are evaluated: (1) uniform; (2) symmetric sinusoidal varying temperature along panel length; and (3) linearly varying temperature through panel thickness. The influence of these three temperature distributions on limit-cycle motions and flutter boundaries of a simply supported 2D panel is investigated.

Mei, Chuh↗
NASA NTRSDate not supplied

Gradient Based Optimization of Chaotic Panel Flutter

This work considers the gradient-based optimization of an aeroelastic panel structure undergoing chaotic vibrations. A previously-presented adaptive time-marching scheme is used to stabilize the design sensitivities which would normally grow unbounded in time, owing to intermittent unstable eigenvalues of the Jacobian. The design optimization entails forcing the root mean square (RMS) of the panel vibration to some specified value, in a way that minimizes the deviation of the structural thickness variables from their uniform baseline values. Depending on the location of the RMS constraint, the output physics maybe chaotic, limit cycle oscillations, or statically buckled.

Bret Kennedy Stanford↗
NASA NTRS1975

Panel flutter optimization by gradient projection

A gradient projection optimal control algorithm incorporating conjugate gradient directions of search is described and applied to several minimum weight panel design problems subject to a flutter speed constraint. New numerical solutions are obtained for both simply-supported and clamped homogeneous panels of infinite span for various levels of inplane loading and minimum thickness. The minimum thickness inequality constraint is enforced by a simple transformation of variables.

Pierson, B. L.↗
NASA NTRS1973

Further discrete variable results for a panel flutter optimization problem

Numerical solutions are presented for the problem of minimum weight design of a thin one-dimensional, simply supported, solid panel in compression, with one side exposed to a parallel high supersonic air flow. The flutter speed is held fixed and a minimum thickness constraint is imposed.

Pierson, B. L.↗
NASA NTRS1972

On the calculation of panel flutter boundaries.

Methods are described for the complete automation of flutter boundary calculations when the aerodynamic forces are derived from linear three-dimensional unsteady potential flow theory. The usual process of visual curve fairing in the mass ratio versus structural damping plane is replaced by numerical procedures for ordering the eigenvalues in such a way that the n-th eigenvalue is always associated with the same flutter boundary. The mass ratio versus structural damping curves are interpolated via parametric cubic spline functions to produce the desired plots in the stiffness-parameter/mass-ratio plane. The entire process is accomplished in a single computer run.

Gaspers, P. A., Jr.↗
NASA NTRS1975

Boundary-layer effect in panel flutter

The present note shows that if the supersonic Mach number is not too large, an analytical expression can be obtained for the generalized aerodynamic force relating the pressure fluctuation at the surface of a flexible plate to the plate displacement in the presence of an adjacent boundary layer. The low supersonic Mach numbers are the ones of maximum interest since it is in this Mach number region that the boundary layer has the most influence. In this respect, Dowell (1971) has already shown that the presence of a boundary layer causes about a 300% increase in flutter dynamic pressure at a Mach number of about 1.2, while it causes only about a 20% increase at a Mach number of 2.

Goldstein, M. E.↗