USE OF EXPERIMENTAL STEADY-FLOW AERODYNAMIC PARAMETERSnIN THE CALCULATION OF FLUTTER CHARACTERISTICS FORnFINITE-SPAN SWEPT OR UNSWEPT WINGS ATnSUBSONIC, TRANSONIC, ANDnSUPERSONIC SPEEDS

摘要

Flutter calculations for several swept and unswept wings through the transonic speed range have been made by the modified strip-theory method of NACA RM L57L10, which employs steady-flow aerodynamic param¬eters for the undeformed wing. Experimentally determined distributions of steady-flow aerodynamic parameters for the undeformed wings were used in the present calculations. Comparisons of these calculated results with experimental flutter data and with calculations previously made by using linearized-theory aerodynamic parameters indicate that the method employed gives accurate flutter results for swept wings at subsonic, transonic, and supersonic speeds. However, since this method of flutter calculation is not applicable when the Mach number component normal to the leading edge is near 1.0, it appears that the transonic flutter characteristics of unswept wings cannot be calculated by the method as given in NACA RM L57LIO. An attempt was made to remove this limitation by using experimental values of two-dimensional lift-curve slope (instead of theoretical values) in the calculation of circulation functions when the Mach number component normal to the leading edge was near 1.0. Applying this procedure to two unswept wings removed the spurious asymptotic rise of flutter speed near Mach number 1.0, but it did not result in very close agreement between calculated and experimental flut¬ter speeds.