With many decades of research devoted to the intriguing nature of vortex-induced vibrations, the offshore industry is constantly looking for new effective solutions in predicting VIV of slender marine structures such as riser pipes. These structures are very sensitive to excitations induced by vortex shedding, which results in vibrations that in certain combinations of waves and current develop into a structural resonance phenomenon known as lock-in. This kind of vibrations can be destructive to some structures and lead to collapse. Many of VIV aspects are far from being understood and advanced modelling is required to investigate the impact of the phenomenon, which significantly affects the service life of marine structures. The main objective of this research is to contribute to the family of semi-empirical models used for prediction of vortex-induced vibrations, with emphasis on low mass ratio elastically supported cylinders capable of moving in cross-flow and in-line directions. In this work a new two degree-of-freedom wake oscillator model has been developed, where vortex-induced lift and drag forces were modelled with two nonlinear self-excited oscillators of van der Pol type. Phenomena exclusive for two degreeof- freedom motion at low mass ratios were examined in detail. Computational fuid dynamics was applied to the problem in order to tune the model parameters. Twodimensional flow past an elastically supported cylinder was considered, and CFD simulation results were used to calibrate the wake oscillator model predictions of the complex fluid-structure interaction.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:680999 |
| Date | January 2016 |
| Creators | Postnikov, Andrey |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=229013 |
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