Numerical investigation of flow-induced vibrations of cylindrical structures

To expand the understanding of flow past and flow-induced vibrations of circular cylinders under complex flow conditions, extensive investigation through two- and three-dimensional numerical simulations are conducted in this thesis. The thesis starts with a two-dimensional numerical study to investigate the effect of a plane boundary on vortex-induced vibrations of circular cylinder both in transverse and inline direction subject to oscillatory flow. The effects of the gap between circular cylinder and plane boundary and Keulegan–Carpenter (KC) number on VIV are discovered. Next, the study is extended to investigate the effect of high-speed rotation on the vortex-induced vibration of the cylinder in the cross-flow direction subject to uniform flow using two-dimensional numerical simulations. The amplitude response is classified in to different regimes both as a function of reduced velocity and rotation rate. In order to better understand the dynamics of rotating cylinder, three-dimensional numerical simulations are performed next for a range of high-speed rotation rates and Reynolds number from Re=100 to 500 under uniform flow conditions. The results of the study are presented in the form of map between rotation rate and Reynolds number identifying different flow structures as a function of rotation rate and Reynolds number. A detailed analysis of flow structures is also presented in order to improve the understanding of the physics of the rotating cylinders. The study is further extended to three-dimensional numerical investigation of flow-induced vibrations of rotating circular cylinders at Re=500 in the cross-flow direction subject to uniform flow. It is found the rotation rate has significant effect on the ‘Lock-in’ regime as the rotation rate is increased. In addition, three-dimensional numerical simulations are carried out next to investigate the VIV around two circular cylinders in side-by-side arrangement to study the effect of gap ratio on the interference between two cylinders