An experimental investigation of the vortex-excited vibrations of pivoted tapered circular cylinders in uniform and shear flow

A systematic experimental investigation to understand the effect of flow and structural non-uniformity on vortex-excited vibrations is underway at the University of Notre Dame's Hessert Center for Aerospace Research. The experiments are designed to investigate the effects of axial taper of a circular cylinder and its interaction with shear in the approach flow on the structural response to vortex shedding. The dynamic response characteristics of a pivoted, tapered circular cylinder subjected to vortex-excited vibrations in a wind tunnel are reported here. In all, six scenarios of tapered pivoted cylinders in uniform and shear flows were investigated. The salient features of the experimental investigations and the experimental observations are presented here as time histories of the structural displacements, structural response amplitudes as a function of flow speed and power spectral densities of the near wake velocity fluctuations. The results of the experimental investigations indicate that the response of axially varying structures to vortex-excited vibrations is quite different from those of uniform cylinders (Balasubramanian et al., J. Fluids. Struct. 14 (2000) 65). The range of locked-in structural response is found to be very sensitive to the relative orientation between the flow-gradient and axial taper of the cylinder.