Study of the vortex-induced vibrations in off-shore structures

The flow around different geometric obstacles is a challenging research topic. The continual change of flow separation points positions on the obstacle surface generates the vortices in downstream flow within a phenomenon called vortex shedding, which was originally discussed by Mr. von K ́arm ́an. Because of this continuous relocation of separation points on the obstacle surface, both the pressure and forces differ in an unstable scenario on the obstacle surface. The occurrence of oscillations or so-called vortex-induced vibrations in obstacle therefore takes place. These vortex-induced vibrations may cause real disasters. A well-known example is the Tacoma Narrows Bridge – USA in 1940. Important applications can be found in many parts of the off-shore structures. This dissertation is giving a deep understanding of the phenomenon by simulating different study cases as well as presenting solutions for reducing the effect of it in deep water risers. The dissertation is presenting a numerical tool as well, which is able to predict computationally the behavior of the deep water risers under the mentioned phenomenon. A coupling between a fluid dynamics solver and a structural dynamics solver has been presented based on the available OpenFOAM libraries. A number of fundamental cases had been simulated in the present dissertation for the purpose of validation and deep understanding, while the related theory has also been discussed. The presented solver as well as the design solutions is supposed to be a milestone in an in-depth research regarding this field of deep water risers and off-shore structures. The results of this work may provide more understanding of the presented problems and opened new doors for future work.


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