The design, assembly and testing of a large scale model riser for vortex induced vibrations

Stone, Gillian Anne (2008) The design, assembly and testing of a large scale model riser for vortex induced vibrations. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (10MB)

Abstract

Offshore oil and gas exploration has been moving into ever increasing water depths. On the East Coast of Canada exploration is being done in depths of up to 2,000m in the Orphan Basin region and deepwater exploration and development is ongoing in the water zones of 56 countries worldwide, in and adjacent to every continent. -- Marine risers are pipes used to transport oil and gas from producing fields to surface platforms, tanker loading systems or back down to the ocean floor for export through a subsea pipeline. One of the growing issues facing deepwater risers is Vortex Induced Vibration (VIV), or large amplitude oscillations which occur when the vortex shedding frequency is approximately equal to the structures' natural frequency. -- The focus of this research was to design, assemble and test a Large Scale deepwater riser model (130m in length) for VIV for two main purposes. The first was to be a learning process for the VIV team at Memorial University with the insight gathered in designing and assembling a large scale model in a field situation being invaluable to future projects. The second was through the development of the large scale model, to provide an intermediate step between the common riser models (8-10m in length) that have mainly been used to research and predict VIV to date and the actual 3,000m deepwater risers currently being used in industry. -- The Large Scale Model Riser (LS - Model Riser) that was developed was relatively robust and the assembly and testing went well. Small changes in the parts, instrumentation and assembly process were necessary to aid in assembly and to help the model function properly. The LS - Model Riser was to be outfitted with 65 modules along its length, however, due to problems during assembly and testing, only 28 of those modules were operational during testing. It was felt that although the large drop out rate was unfortunate, the working modules were still located along the entire length of the model and would yield useful data, so testing was carried out with the remaining 28 working modules. The resulting data that was collected was analyzed and determined to be useful, proving that the model could be used as a base for future VIV analysis projects.

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