Experimental investigation of the damping of structural vibrations by vorticity production

Abstract

An experimental investigation has been made of the damping of a plate vibrating at zero angle of attack to a nominally steady, high Reynolds number mean flow. The plate is perforated with a distribution of small circular apertures in which vorticity is produced by the unsteady loading of the plate. The kinetic energy of the vorticity is swept downstream by the flow. Damping occurs by the transfer of energy from the plate to the vortex field provided the Strouhal number ωR/U, based on the radian frequency ω of the vibration, the aperture radius R and the mean stream velocity U, lies between about 0·4 and 0·8. The peak attenuation is of the order of 5 dB relative to an identical unperforated plate. The results are interpreted in terms of recent calculations of the unsteady flow through an aperture in the presence of mean flow, and are expected to be relevant to the alleviation of fatigue failure of aerodynamic control surfaces such as jet nozzle flaps. © 1999 Academic Press.