Subsonic Flutter of Panels on Continuous Elastic Foundations

The subsonic aeroelastic stability of a two-dimensional panel resting on a continuous elastic foundation was investigated. Tests were conducted experimentally on a 104- X 24- X 0.018-in. rectangular aluminum panel in a low-speed wind tunnel. Definite flutter of a traveling-wavetype was observed. Films and oscillograph records were taken. Theoretically, a finite-panel, two-mode, standing-wave analysis was shown to give essentially the same behavior as the infinite-panel, traveling-wave analysis of Miles for this panel. Although a mild, divergence-type instability exists for these panels, the principal instability was shown to be of a traveling-wave, flutter-type. Comparison of experiment and theory showed good agreement in flutter speed and wavelength but poor agreement in wave speed and frequency at flutter. This discrepancy was attributed to limitations in the test set-up as well as to the general difficulty of predicting the wave speed and frequency as accurately as the flutter speed. The present investigation should be of interest in problems of hydroelastici ty, axially symmetric cylinders, and inflatable structures at low speeds, as well as to panels lying on springy elastic materials*