Session: 15-05-01 Mooring, Riser and Pipelines

Submission Number: 180518

Technical Feasibility Analysis of a New Web-Type Mooring Layout 

Y-type branching is an effective load‐bearing topology, which can be pervasively observed in nature, such as on leaf and wing venation, spider webs, etc. It offers multiple concurrent load paths to share the loads. Inspired by the anchoring system of spider webs, a novel Web-type taut-mooring system consisting of main lines and Y-type branches is proposed in this study. It is supposed to reduce the anchors at the seabed, hence reduce the cost of installation. The objective of this study is to evaluate the performance of this Web-type mooring system when it applies to moor offshore floating platforms. The hypothesis for this new mooring system includes: 1) reduce the motion responses of a platform, and 2) achieve peak shaving in mooring-line tensions via load diversion from a main line to its branches.

This new Web-type mooring system is then applied to moor OC6, a semi-type floating offshore wind turbine. Numerical simulations are performed to compare a conventional radial mooring layout against the proposed Web-type one under an equivalent pretension, axial stiffness, immersion angle, fairlead geometry, and draft. Dynamic responses are computed using OrcaFlex, and the second-order wave loads are considered in the time domain calculations.

The simulations results show that the motion responses, including surge, heave and pitch, do not present a notable difference with the new Web-type mooring across various sea states and headings. However, yaw motion exhibits a modest increase with the new layout, causing by a reduced yaw lever and enhanced surge/sway–yaw coupling effect. Most importantly, the Web-type layout delivers a systematic load redistribution: the tension on main lines is subject to a significant reduction under various heading conditions, while the two adjacent sub-lines absorb substantial mooring tension, evidencing effective peak shaving effects by Web-type layout. Overall, the biomimetic topology of the new Web-type mooring layout shows an excellent performance in mitigating mooring line tension while enabling potential anchor-count reduction. It could offer a safe and environmentally mooring solution for very large floating systems, such as floating PV farms.

Presenting Author: Zhi-Ming Yuan University of Strathclyde

Presenting Author Biography: Dr. Zhiming Yuan is a Reader (2022 - ) in the Department of Naval Architecture, Ocean and Marine Engineering at the University of Strathclyde. He is the Director of postgraduate teaching programme. His research activity mainly focused on Hydrodynamics and Ocean Renewable Energy, and he has published more than 90 peer-reviewed journal articles on these areas. Dr Yuan is currently acting as the Deputy Editor of Ocean Engineering, Scientific Managing Editor for Ocean Engineering, Associate Editor of Frontiers in Energy Research and editor board member of several international journals. He is an ITTC committee member and chair of ITTC Maneuvering Committee, and the Director of the Hydrodynamics and Ocean Renewable Energy Laboratory (HOREL) at Strathclyde. His research work on wave interference has been selected as Focus on Fluids article by Journal of Fluid Mechanics, and highlighted by Nature (Nature. 565(7741):538), and been widely reported by TheTimes, DailyMail, Today Headline, ScienceNews, 知识分子, etc. In 2022, he received the 32nd Ig Nobel Prize in the field of physics for “trying to understand why ducklings are swimming in formation”.

Authors:

Kaiming Yang University of Strathclyde
Bingchen Liang State Key Laboratory of Coastal and Offshore Engineering, Ocean University of China
Xun Meng State Key Laboratory of Coastal and Offshore Engineering, Ocean University of China
Shuang-Rui Yu University of Manchester
Zhi-Ming Yuan University of Strathclyde