Thesis

VIV studies in hydrodynamic testing of towed long slender cylinders

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Awarding institution
  • University of Strathclyde
Date of award
  • 2018
Thesis identifier
  • T14983
Person Identifier (Local)
  • 201274083
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • The thesis presents experimental and theoretical work on VIV and fatigue damage during the tow operation for installation of free standing risers. The research studies were sponsored by PEMEX, the Mexican national oil company and the Mexican Science and Technology National Council, within a professional development program, to assist with the short-term execution of deep water projects, considering the potential of important findings in the Gulf of Mexico, and the decreasing opportunities of easy access reservoirs as well as the production declination in the main oilfields in shallow waters. A literature review on related VIV fundamentals was conducted while approaching industry leaders in the execution of tow-out installation methods, to assimilate some of the main processes during engineering, fabrication and towing operations for installation of pipe bundles and risers, which supported initial modelling works for towing simulations to explore VIV prediction tools. After revision of industry standards and published work related to design guidelines on VIV and fatigue damage, the contribution to knowledge in the present work was focused on the evaluation and implementation of innovative technologies for instrumentation and response measurement in model testing, looking for a better understanding and characterisation of responses for more representative models of full-scale designs, with hydrodynamic parameters and coefficients required for calibration of the different prediction models used in leading software for VIV and fatigue analysis. The experimental work used one of the first implementations of an underwater optical tracking system for motion capture, to conduct hydrodynamic studies over flexible submerged elements, as well as the first design and installation of a fibre optic sensing system in the towing tank of the University. The successful instrumentation, allowed measurement and data processing for results which contribute to understanding of some of the response characteristics for a flexible model with a long aspect ratio, subject to selected loading conditions of interest for current flows, regular waves, change of initial tension and tow depths, presenting indications of interesting VIV phenomena such as transition branches and vortex shedding modes, allowing the identification of velocity boundaries to avoid high response amplitudes associated to the upper branch response of VIV. Future work and test conditions are proposed to develop the potential of the evaluated technologies to achieve a high-quality data acquisition system for further VIV studies overflexibles elements. The research work achieved a successful application of an aerial motion capture system in flexible beams and a first implementation of the technology on VIV studies using underwater cameras with integration of a fibre optic sensing system for strain/curvature measurements. These were applied in the final experimental work over a model tested in the towing tank at the Kelvin Hydrodynamics Laboratory, with an aspect ratio about 430, a final mass ratio of 0.9, damping ratio in still fluid ζ = 0.046 (m*ζ=0.04), for combinations of current and wave flows at low Keulegan-Carpenter number range of 0.3 < KC < 5.25. The results provide an insight of the response behaviour for the main fluid loading conditions during towing operations for offshore installations and route planning, as well as methods and basis for further research development with a sound potential of application.
Advisor / supervisor
  • Barltrop, N. D. P. (Nigel D. P.)
Resource Type
DOI

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