Experimental investigation of vortex-induced oscillations in flow past bluff bodies

The objective of this research is to investigate vortex-induced oscillations in flow past bluff bodies. In this thesis, the results of experiments on the cross-flow oscillations of bluff bodies in water are presented and discussed. The investigation was aimed at establishing the effects of geometry, surface characteristics, aspect ratio, end plates and hydrodynamic parameters on the nature and extent of these resonant oscillations.;An experimental system was developed to measure the amplitude and frequency of resonant oscillations of submerged bluff bodies. Shapes tested included spheres, back-to-back cones, cones with different orientations, cylinders with hemispherical caps, circular cylinders and cubes. Tests were carried out over a range of mass ratios. The effects of surface characteristics were examined over a velocity range. The effects of aspect ratio and end plates were tested to compare with other experimental work.;The results showed that the sharp tail and the orientation of models have prominent effects on cross-flow oscillations. The stable shapes include type I cone, type I cap and cube. Such a sharp configuration has no afterbody for the fluctuating lift forces to act on. Increasing the length-to-width ratio reduces the vibration amplitude. The hairy surface has the most stabilizing effect among the surface characteristics because the hair disrupts the formation of vortices and increases the damping ratio. The oscillation amplitude and frequency response were also studied. The mass ratio and damping ratio affect transverse resonant vibrations and end plates reduce the three-dimensional effects. (Abstract shortened by UMI.)...