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Vortex-induced motion of a free-standing riser below the critical mass ratio

Citation

Florager, C and Balash, C, Vortex-induced motion of a free-standing riser below the critical mass ratio, Proceedings of the ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering, 25-30 June 2017, Trondheim, Norway, pp. V002T08A032-039. ISBN 978-0-7918-5764-9 (2017) [Refereed Conference Paper]

Copyright Statement

Copyright 2017 ASME

DOI: doi:10.1115/OMAE2017-61399

Abstract

The presented work studied the vortex-induced motion (VIM) response of a free-standing riser (FSR) with varied riser length and buoyancy can (BC) mass with an ultimate aim to find a combination that would reduce the motion of the system. Specifically, four model configurations were experimentally tested in a flume tank over a range of flow velocities, with the BC motion recorded by a submersible camera positioned directly above the model; consequently, inline (IL) and crossflow (CF) amplitudes were estimated with a motion tracking software. In the pre-resonant flow regime, non-dimensionally, minimal differences were observed between the CF amplitudes, and the IL motion was reduced with a longer riser. Given the extreme length of full-scale FSRs and inherent low natural frequency, it is impractical to increase the riser tension to a point where VIM would not occur under normal environmental conditions. Alternatively, increasing the mass ratio of the BC so that it is above the critical mass ratio of 0.54 (the ratio of the mass of the body to the mass of the fluid) would limit the resonant flow velocities to a finite range, but a larger BC may not be an economically viable solution, and because of the increased diameter, it would experience a larger CF amplitude during resonance. Further study into the prevention of VIM of an FSR by varying the riser length and BC mass is unlikely to be beneficial.

Item Details

Item Type:Refereed Conference Paper
Keywords:risers (casting), vortices, pipeline risers
Research Division:Engineering
Research Group:Maritime Engineering
Research Field:Ship and Platform Structures
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in Engineering
Author:Florager, C (Mr Curtis Florager)
Author:Balash, C (Dr Cheslav Balash)
ID Code:124327
Year Published:2017
Deposited By:NC Maritime Engineering and Hydrodynamics
Deposited On:2018-02-19
Last Modified:2018-04-20
Downloads:0

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