Experimental investigation of the damping of structural vibrations by vorticity production

An experimental investigation has been made of the damping of a plate vibra ting at zero angle of attack to a nominally steady, high Reynolds number me an flow. The plate is perforated with a distribution of small circular aper tures in which vorticity is produced by the unsteady loading of the plate. The kinetic energy of the vorticity is swept downstream by the flow. Dampin g occurs by the transfer of energy from the plate to the vortex field provi ded the Strouhal number omega R/U, based on the radian frequency omega of t he vibration, the aperture radius R and the mean stream velocity U, lies be tween about 0.4 and 0.8. The peak attenuation is of the order of 5 dB relat ive to an identical unperforated plate. The results are interpreted in term s of recent calculations of the unsteady flow through an aperture in the pr esence of mean flow, and are expected to be relevant to the alleviation of fatigue failure of aerodynamic control surfaces such as jet nozzle Baps. (C ) 1999 Academic Press.