Unsteady Loading and Dynamic Response of a Structure Excited by a High-Speed Wall-Bounded Jet Part Ⅱ: Structural Response

摘要

An exhaust structure in a modern embedded propulsion system, if not designed carefully, can experience high-cycle fatigue failure from excessive vibrations induced by the unsteady pressure loading from the high-speed jet Part Ⅰ presented the results from an experimental study on the aerodynamic characteristics of the jet and the unsteady pressure loading on a rigid deck surface. The present paper discusses the results obtained from an experimental set up called, "structural deck", which characterized the vibratory responses of a plate at multiple flow speeds ranging from subsonic to supersonic Mach numbers. Results show that the vibratory energy of the structural deck plate peaks at a transonic flow speed. This is postulated to be attributable to the aerodynamic coincidence between the characteristic structural waves and the convecting turbulence in the impinging shear layer whose effective strength reaches a maximum at this flow speed. Furthermore, the damping associated with the dominant plate mode shows a dip in the transonic flow speed range, indicating a flutter-like aero-elastic interaction.