Book Description

A systematic analytical procedure has been developed for computing flutter characteristics of rectangular panels with stream-aligned side edges, based on air forces from three-dimensional linearized supersonic unsteady potential flow. The procedure has particular usefulness in the low supersonic speed range where static and quasi-static aerodynamic approximations are considered to be least valid and can provide bases of comparison for some of the simpler types of analysis. The panel is considered to be finely divided into many boxes, and the aerodynamic influence coefficients between all pairs of boxes are obtained by numerical integration. The flutter analysis is a modal type, which readily coordinates with the aerodynamic box method, and can be used for calculating the flutter stability of any flat or nearly flat panel, whether of isotropic or anisotropic stiffness, and of buckled panels for which the flutter is a small-amplitude, simple harmonic, superimposed motion to which linear theory is applicable. A number of results are presented for flat unstressed, isotropic panels with simply supported edges and with clamped edges. For clamped-edge aluminum panels with length-width ratio of 2 at sea level, the panel flutter parameters are tabulated for eight Mach numbers ranging from 1.02 to 2.0. For Mach 1.3, fluter boundaries are plotted for length-width ratios from 0 to 10 for simply supported edges and from 0 to 4 for clamped edges so that design values can be read for a wide range of panel materials and air densities. Appendix A delineates the way in which the natural mode characteristics were developed for calculating the presented flutter results without the need for double-precision arithmetic. Appendix B provides formulas for conversion among a number of types of flutter solution parameters in current use. Appendix C describes a way to economize computer time for the large matrix multiplication required.