Prøveforelesning
Se prøveforelesningBedømmelseskomité
Professor Charles H.K. Williamson, Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, USA
Head of Research Department Kjetil Skaugset, StatoilHydro Research Centre
Professor Bjørn Gjevik, Matematisk institutt, Universitetet i Oslo
Leder av disputas: Kristian Ranestad
Veileder: Prof. John Grue, Dr. Atle Jensen
Sammendrag
The present work has been carried out at the Mechanics
Division, Department of Mathematics, University of Oslo, Norway. Vortex-Induced Vibrations (VIV) is a central fluid-structure interaction problem in the offshore oil industry. For example, under the action of marine currents the long pipe-lines conveying the oil and gas from the extraction sites to the Norwegian coast can oscillate up and down and eventually be damaged.
The interaction between a rigid circular cylinder mounted on springs and a transverse current (perpendicular to the cylinder axis) was investigated using flow visualization techniques. Until 2004 most studies focused on the cross-flow motion only, assuming that the effect of streamwise (parallel to the flow) vibrations was negligable. We designed mountings that allowed the cylinder to move in both directions simultaneously
and studied the effect of this additional degree of freedom on the cylinder response.
The results show that the presence of streamwise oscillations can modify the amplitude of vibrations and the range of resonance depending on the ratio between the natural frequencies in both directions. Integrating those results in the prediction models used in this industry would help preventing VIV problems.
Kontaktperson
For mer informasjon, kontakt Marie Wennesland.