Restriction lift date: 2026-05-31
Experimental and numerical investigation of towing operations for large floating offshore wind farms
Loading...
Files
Date
2024
Authors
Chitteth Ramachandran, Rahul
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
Floating Offshore Wind Turbines (FOWTs) represent a pivotal advancement in renewable energy technology, extending the reach of wind power to previously inaccessible waters. Their importance lies in their ability to exploit the stronger and more consistent winds in deep waters. Installing these floating platforms in sites where the weather is harsh invites significant challenges. A major challenge lies in towing these platforms from the fabrication site to the farm location. The commercialisation of floating wind aims at farm-scale deployments and installation of large wind turbines. For planning fast, cost-effective and safe towing operations, the understanding of its physics is paramount. It is also important to develop numerical methods and simulation approaches to understand and predict the motions and towing loads while towing these significant floating structures. This thesis constitutes a deep exploration of the towing operations associated with floating wind turbines, integrating a multifaceted analysis encompassing case studies, experimental tests and numerical methodologies. Semi-submersible floaters, being one of the early movers, are the main focus of this thesis.
The presented thesis has followed an ‘industry-ready’ approach and aims at minimising the gap between academia and industry by attempting an equilibrium between them. The thesis is split into four research papers and starts with a literature review examining marine operations integral to floating wind turbines, identifying specific challenges and finding opportunities for synergy with other well-established and developed offshore industries such as Oil and Gas (O & G) and fixed-bottom wind industries. Towing operations, being required for installation, major repairs and decommissioning are then analysed and two numerical approaches for the hydrodynamic analysis of semi-submersible floating wind turbines are developed and implemented in two different commercial hydrodynamic analysis tools. The first method is a potential flow-based forward speed approach with corrections for viscous effects implemented in the in-house tool SEACAL. The second method is a hybrid approach utilising a potential flow method combined with the Morison equation and implemented in the commercial tool Orcaflex. The hybrid approach is also implemented in a free open-source numerical tool OpenFAST for the further development of the research work. To validate the numerical results, a detailed experimental campaign was conducted and validation data for towing in various sea conditions, towing configurations and towing speeds were generated. A comparative study of both approaches is presented and the advantages and disadvantages of the developed methods are summarised. The findings indicate that both developed numerical models possess the capability to analyse and predict towing characteristics contingent upon towing speed and prevailing wave conditions. The first method is better suited to considering low speeds (0.514 m/s–1.542 m/s) and low wave heights (1m – 2m) whilst the second method is better suited for higher speeds (0.514 m/s – 3.084 m/s) and higher wave heights (1m – 6m). Depending on the weather conditions, towing requirements and availability of the numerical tools, the suitable analysis method can be chosen.
Description
Keywords
Floating offshore wind farms , Marine operations , Towing , Hydrodynamics
Citation
Chitteth Ramachandran, R. 2024. Experimental and numerical investigation of towing operations for large floating offshore wind farms. PhD Thesis, University College Cork.