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Hydrodynamics and Mooring Analysis of Floating Structures
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Hydrodynamics and Mooring Analysis of Floating Structures

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Ocean Engineering".

Deadline for manuscript submissions: closed (5 August 2024) | Viewed by 25282

Special Issue Editors

Dr. Shan Wang

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Guest Editor
Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Tecnico, Lisbon, Portugal
Interests: CFD; fluid-structure interaction; mooring analysis; naval hydrodynamics; slamming; ship vibration; floating production system; hydro-elastic response
Special Issues, Collections and Topics in MDPI journals
Dr. Carlos Guedes Soares

E-Mail Website
Guest Editor
Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Interests: marine environment; ship dynamics; marine structures; safety and reliability
Special Issues, Collections and Topics in MDPI journals
Dr. Philipp R. Thies

E-Mail Website
Guest Editor
Renewable Energy, University of Exeter, Penryn, Cornwall TR10 9FE, UK
Interests: reliability engineering; component testing; offshore renewables; hydrodynamic modeling; innovative mooring systems
Prof. Dr. Yushun Lian

E-Mail Website
Guest Editor
College of Harbour, Harbor Coastal and Offshore Engineering, Hohai University, Nanjing 210098, China
Interests: mooring and anchor technology for ocean structures; wave energy converters; wind farms; marine ranching; fiber rope for space elevator; mechanical behaviors of fiber ropes

Special Issue Information

Dear Colleagues,

Current research and development activities for a range of floating offshore structures are being developed to support the world's energy and resource requirements. Understanding the fundamental hydrodynamic forces in the offshore environment is crucial to the success of future projects. Not only are floating platforms subject to loading from ocean waves, but also increased motion due to the wave–body interactions.

There is a variety of offshore structures, including renewable energy devices and aquaculture installations that require mooring systems to be kept in position. These floating structures are continuously subjected to environmental loadings from waves, currents, wind, etc. The motion response of floating structures is of great concern in marine engineering and in design of moorings for offshore structures. The dynamic nature of wave loads, and the non-linear response of moored structures is a complex problem. In addition, in order to develop a floating aquaculture with a mooring system which could meet global demand, increasing the cultivation capacity for fish production is also a priority. Designing floating net cages and mooring systems is of great concern to the marine aquaculture industry due to the potential structural failures in waves and currents during storm events.

To understand the hydrodynamics of floating structures with moorings, researchers have developed and applied several distinct approaches, including but not limited to model tests, numerical modelling based on potential-flow theory and computational fluid dynamics. The present Special Issue of the Journal of Marine Science and Engineering covers a broad scope of hydrodynamics and a mooring analysis of various floating structures. We encourage the submission of high-quality papers in the following areas:

  • Hydrodynamics of floating bodies;
  • Wave-induced loads on floating bodies;
  • Innovative mooring design and analysis;
  • Optimization of floating renewable energy devices;
  • Offshore platforms;
  • Numerical solutions;
  • Computational fluid dynamics;
  • Model tests;
  • Reliability analysis;
  • Extreme response;
  • Offshore aquaculture systems.

Dr. Shan Wang
Dr. Carlos Guedes Soares
Dr. Philipp R. Thies
Prof. Dr. Yushun Lian
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Marine Science and Engineering is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hydrodynamics
  • mooring dynamics
  • offshore platforms
  • offshore renewable energy
  • renewable energy devices
  • mooring reliability analysis
  • synthetic moorings
  • floating aquaculture
  • floating wind
  • floating tidal
  • floating wave energy

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Published Papers (10 papers)

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Research

17 pages, 12352 KiB  
Article
Optimization of Connection Parameters of Self-Adaptive Modular Floating Wind Farms
by Yuming Zhang, Da Li and Haixiao Liu
J. Mar. Sci. Eng. 2024, 12(10), 1840; https://doi.org/10.3390/jmse12101840 - 14 Oct 2024
Viewed by 682
Abstract
Connection parameters are the key factors influencing the responses of modular floating structures; due to the complexity of structural response properties, the assessment and optimization of connection parameters are still vital issues in designing modular floating structures. In the present work, for a [...] Read more.
Connection parameters are the key factors influencing the responses of modular floating structures; due to the complexity of structural response properties, the assessment and optimization of connection parameters are still vital issues in designing modular floating structures. In the present work, for a novel structural configuration of self-adaptive modular floating wind farms based on existing works from the case of a mobile offshore base, a quantified approach for the assessment of connection parameters is established based on frequency domain numerical analysis taking into account both the economic effects and generalized performance. Based on the quantified assessment, an optimization process is carried out, to obtain a connection parameter combination. From the optimized connection parameters, it can be found that the most appropriate tri-axial stiffness according to present studies is in the magnitude from 1 × 106 to 7 × 107 N/m, and the damping ratio is close to 1.0 for most connection structures. By contrast with feasible uniform connection parameters, the optimization methodology is confirmed to be able to reduce both connection parameters and responses. Then, a time domain approach for the calculation of motions of interconnected modular floating structures taking into account geometry nonlinearity is proposed and obtained in good accordance with the frequency domain results, and the effectiveness of both the frequency domain and time domain is validated. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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20 pages, 8549 KiB  
Article
Experimental Characterization of Stiffness of a Polyester Mooring Rope for a CFPSO
by Limei Feng, Qian Wang, Shan Wang and Sheng Xu
J. Mar. Sci. Eng. 2024, 12(8), 1435; https://doi.org/10.3390/jmse12081435 - 20 Aug 2024
Viewed by 882
Abstract
Synthetic ropes are increasingly favored for use in offshore systems. Accurate predictions of the coupled hydrodynamic performance and structural response of offshore structures depends on a thorough understanding of the nonlinear characteristics of fiber materials. The objective of this study is to experimentally [...] Read more.
Synthetic ropes are increasingly favored for use in offshore systems. Accurate predictions of the coupled hydrodynamic performance and structural response of offshore structures depends on a thorough understanding of the nonlinear characteristics of fiber materials. The objective of this study is to experimentally characterize the stiffness of a polyester mooring rope for a cylindrical floating production storage and offloading system. The quasi-static stiffness of the ropes and aged ropes after installation and the dynamic stiffness in various loading conditions were computed based on sub-rope tests following the guidelines from the American Bureau of Shipping. The quasi-static stiffness curves exhibited a linear decrease in values as the logarithm of the loading period (in minutes) increased. The dynamic stiffness was, in general, much higher than the quasi-static stiffness. The dynamic stiffness under various loading conditions revealed the complexities of the mechanical properties of polyester rope. Parameters such as the mean load, load amplitude, loading period, and loading cycles all had a notable impact. More tests are required to have a better understanding of their effects. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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20 pages, 4662 KiB  
Article
Effects of Mooring Line with Different Materials on the Dynamic Response of Offshore Floating Wind Turbine
by Yushun Lian, Fan Zhong, Jinhai Zheng, Wenxing Chen, Gang Ma, Shan Wang and Solomon C. Yim
J. Mar. Sci. Eng. 2023, 11(12), 2302; https://doi.org/10.3390/jmse11122302 - 5 Dec 2023
Cited by 1 | Viewed by 2021
Abstract
The influence of mooring systems with lines of different material on the dynamic response of a floating wind turbine is studied using a 5 MW OC4-DeepCwind semi-submersible wind turbine as a representative prototype in this study. Two types of mooring systems were designed [...] Read more.
The influence of mooring systems with lines of different material on the dynamic response of a floating wind turbine is studied using a 5 MW OC4-DeepCwind semi-submersible wind turbine as a representative prototype in this study. Two types of mooring systems were designed using the MoorDyn module in OpenFAST software (v3.1.0): one uses chains, and the other uses a hybrid mooring line composed of chains and high-strength polyethylene (HMPE) ropes. A wind turbine with two types of mooring systems was simulated using the OpenFAST software. The results show that the floating wind turbine moored with the hybrid lines exhibited a larger heave and pitch motion than that moored using chains alone. At the same time, the surge displacement was smaller than that of the wind turbine using chains alone. In terms of mooring line tension, the mean and amplitude values of the hybrid mooring system at the location examined were smaller than those of the chain mooring system. Thus, using HMPE ropes in the mooring system can significantly reduce line loads. In addition, the HMPE ropes used in the floating wind turbine mooring system did not affect the power generation of the wind turbine. This study provides promising support data and observations for applying high-strength polyethylene (HMPE) ropes in mooring systems for floating wind turbines. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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18 pages, 14290 KiB  
Article
An Intelligent Monitoring System for the Force Characteristics of Floating Bollards in a Ship Lock
by Linjian Wu, Jia Yang, Zhouyu Xiang, Mingwei Liu, Minglong Li, Yutao Di, Han Jiang, Chuan Dai and Xudong Ji
J. Mar. Sci. Eng. 2023, 11(10), 1948; https://doi.org/10.3390/jmse11101948 - 9 Oct 2023
Cited by 3 | Viewed by 1196
Abstract
Due to the large scale of navigation ships, the fast speed of entering the lock, and the irregular mooring and the complicated flow conditions in the lock chamber, it is common for the floating bollards of the lock to suffer structural damage or [...] Read more.
Due to the large scale of navigation ships, the fast speed of entering the lock, and the irregular mooring and the complicated flow conditions in the lock chamber, it is common for the floating bollards of the lock to suffer structural damage or even failure due to the overloaded mooring force. However, the traditional cable load measurement method cannot offer real-time feedback on force characteristics of floating bollards, making it difficult to accurately judge its service status. To this end, according to the floating bollard structure type and load condition of a representative ship lock project in China, this paper determines the theoretical model parameters of a floating bollard load response based on three-dimensional finite element numerical simulation test data and constructs a modified load response model of floating bollards. On this basis, an intelligent floating bollard monitoring system based on big data, internet, and cloud services is developed to intelligently perceive real-time floating bollard force characteristics and monitor the long-term service status. Relying on a representative ship lock in China, a field test of the floating bollard intelligent monitoring system is carried out. The relative error between the calculated values via the model (i.e., system exhibition results) based on the numerical results and the field-measured values is within 15%. This result verified the accuracy and effect of the monitoring system. This research supports the establishment of the digital perception monitoring platform for ship lock facilities and improves the automation level of ship lock operation and management as well as overall risk prevention and control capabilities. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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22 pages, 7173 KiB  
Article
Coupled Analysis of Hydrodynamic Responses of a Small Semi-Submersible Platform and a Large Floating Body
by Jianye Yang, Jun Yan, Yan Zhao, Jinlong Chen and Heng Jin
J. Mar. Sci. Eng. 2023, 11(7), 1451; https://doi.org/10.3390/jmse11071451 - 20 Jul 2023
Cited by 2 | Viewed by 1582
Abstract
This paper focuses on the hydrodynamic interaction between the large floating body and a small transfer platform in a jettyless floating transfer system. A high-order boundary-element method combined with a direct time-domain-solution method to calculate and analyze the hydrodynamic response of the small [...] Read more.
This paper focuses on the hydrodynamic interaction between the large floating body and a small transfer platform in a jettyless floating transfer system. A high-order boundary-element method combined with a direct time-domain-solution method to calculate and analyze the hydrodynamic response of the small platform while berthed with the fixed large floating body and freely floating large body under wave action was applied and compared with the hydrodynamic response of a single small transfer platform. It was found that when the large floating body and the small transfer platform were both located on the leeward side, they had little mutual influence, and the hydrodynamic response agreed well with that of the single small transfer platform and the single large floating body. While the small platform was located on the leeward side of the large floating body, it significantly affected the hydrodynamic response of the platform, resulting in a significant reduction in horizontal motion and pitch motion, meaning that the shielding effect was significant. Within a certain range of wave periods, the heave-motion amplitudes can be significantly reduced, but beyond that range, they increase. Therefore, it is important to carefully consider the relative motions of LNG transport ships and small platforms when connecting them via aerial jumper pipes in jettyless floating transfer systems. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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29 pages, 16831 KiB  
Article
Dynamic Response of Deep-Sea Trawl System during Towing Process
by Dapeng Zhang, Bowen Zhao, Keqiang Zhu and Haoyu Jiang
J. Mar. Sci. Eng. 2023, 11(1), 145; https://doi.org/10.3390/jmse11010145 - 7 Jan 2023
Cited by 2 | Viewed by 1537
Abstract
The trawl system plays an irreplaceable role in deep-sea fishing. In the towing process of the trawl system, many complex mechanical phenomena occurs, so it is necessary to analyze the dynamic response of the deep-sea trawl system during the towing process. In this [...] Read more.
The trawl system plays an irreplaceable role in deep-sea fishing. In the towing process of the trawl system, many complex mechanical phenomena occurs, so it is necessary to analyze the dynamic response of the deep-sea trawl system during the towing process. In this paper, an equivalent mathematical model for predicating the movement of the ocean trawl system is established based on the equivalent net theory. In the proposed method, the lumped mass method is used to simulate the towed cable and some lines with hydrodynamic characteristics are used to simulate the fishing net. The effects of towing speeds on the dynamic characteristics of a rigid truss trawl system and a flexible trawl system during straight-line towing and rotation towing are studied. The results show that it is possible to simulate trawl motion, and the trawling process is well-presented using this equivalent mathematical model. The disadvantage of this method is also obvious, that is, it cannot simulate trawls with a large number of meshes because the proliferation of mesh numbers can lead to difficult computational convergence. The results also demonstrate that during straight-line towing, the higher the speed, the greater the tension of the cable. Due to the rigid truss, the shape of the rigid truss trawl under different towing speeds is not much different, while the shape of the flexible trawl system changes greatly. During rotating towing, the tension of the cable changes abruptly in the initial stage, and then fluctuates periodically in the time domain. With the increase of towing speed, the overall outward floating distance of the trawl increases gradually. This study has a certain reference and guiding role for deep-sea fishing operations. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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22 pages, 12047 KiB  
Article
Dynamic Response of a SPAR-Type Floating Wind Turbine Foundation with Taut Mooring System
by Gong Xiang, Xianbo Xiang and Xiaochuan Yu
J. Mar. Sci. Eng. 2022, 10(12), 1907; https://doi.org/10.3390/jmse10121907 - 5 Dec 2022
Cited by 7 | Viewed by 2666
Abstract
Compared with the traditional catenary or semi-taut mooring lines, the taut mooring system is more advantageous in many aspects, such as reduction of mooring line loads, erosion and fatigue damage during the powering productions of the floating wind turbines. This paper presents a [...] Read more.
Compared with the traditional catenary or semi-taut mooring lines, the taut mooring system is more advantageous in many aspects, such as reduction of mooring line loads, erosion and fatigue damage during the powering productions of the floating wind turbines. This paper presents a taut mooring system made of synthetic fiber mooring lines, which can experience large elongations for a spar-type floating wind turbine. A finite element method (FEM)-based tensile mooring line model is proposed to study the mooring statics and dynamics of the floating wind turbine. A time domain modelling method coupled with the developed mooring line model is adopted to study the dynamics of a spar-type floating wind turbine foundation moored by the taut mooring system under regular waves. A systematic dynamic response and structural analysis are conducted based on variations in the mooring length and pretension. Additionally, comparative performance analyses are investigated for two mooring configurations with different numbers of mooring lines: two-point and three-point taut mooring system. It is found that factors, such as mooring length, pretension and the number of mooring lines, have significant impact on the in-plane and out-of-plane motion responses of the foundation. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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17 pages, 3091 KiB  
Article
Numerical Study on the Mooring Force in an Offshore Fish Cage Array
by Zhongchi Liu, Shan Wang and C. Guedes Soares
J. Mar. Sci. Eng. 2022, 10(3), 331; https://doi.org/10.3390/jmse10030331 - 26 Feb 2022
Cited by 24 | Viewed by 3832
Abstract
The mooring force in a fish cage array subjected to currents and waves is investigated using the finite element method. Firstly, the numerical model of a fish cage array with six gravity cages is built by Ansys/APDL. Collars and bottom rings are simulated [...] Read more.
The mooring force in a fish cage array subjected to currents and waves is investigated using the finite element method. Firstly, the numerical model of a fish cage array with six gravity cages is built by Ansys/APDL. Collars and bottom rings are simulated with pipe and beam elements while the rest structure is simulated with link elements, including the net and mooring cables. Thus, the weight and hydrodynamic load on the cables can be considered. The initial shape of the mooring ropes is calculated based on mooring dynamics. Since each component is a slender structure in the cage array, the Morison equation is used to calculate the hydrodynamic load. Secondly, the mooring forces are assessed for the system in different sea states. The locations of the maximum mooring force on different parts in the mooring system are found. The mean values and amplitudes of maximum mooring forces on different parts are calculated. The main ropes have the maximum mooring forces under all sea states. The mean values of the maximum mooring forces increase with the current velocity and wave height. When the attack angle is 0° and 90°, the two adjacent bridle ropes do not play the role of pulling the cage together. One is pulled tight and the other one is slack. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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24 pages, 14443 KiB  
Article
Hydrodynamic Performance of a Multi-Module Three-Cylinder Floating Breakwater System under the Influence of Reefs: A 3D Experimental Study
by Jianting Guo, Yongbin Zhang, Xiangqian Bian and Sheng Xu
J. Mar. Sci. Eng. 2021, 9(12), 1364; https://doi.org/10.3390/jmse9121364 - 2 Dec 2021
Cited by 1 | Viewed by 2750
Abstract
As the technical and theoretical research of floating breakwaters is becoming increasingly mature, the floating breakwaters are now being utilized, especially in offshore reefs. Therefore, it is of practical significance to study the hydrodynamic performance of a multi-module floating breakwater system under the [...] Read more.
As the technical and theoretical research of floating breakwaters is becoming increasingly mature, the floating breakwaters are now being utilized, especially in offshore reefs. Therefore, it is of practical significance to study the hydrodynamic performance of a multi-module floating breakwater system under the influence of reefs. In this study, a 3D model experiment was carried out on a system consisting of eight three-cylinder floating breakwater modules under the influence of reefs. A wave attenuation mesh cage was incorporated at the bottom of the model. The floating breakwater system was slack-moored in its equilibrium position, and each module was connected by elastic connectors. The reefs were modeled on a bathymetric map of existing reefs in the East China Sea. In this experiment, the wave transmission coefficients, motion responses, and mooring forces of the floating breakwater system were measured. The results showed that the three-cylinder floating breakwater in the beam waves (β = 90°) has excellent wave attenuating performance under the influence of reefs, especially for short-period waves. However, under the influence of the reef reflection wave and the shallow water effect, the motion responses in the three main stress directions of the floating breakwater were large, and there was some surge and pitch motion. Under the influence of the aggregation and superposition of reflected waves on both sides of the reefs, the peak mooring forces in the middle position of the floating breakwater system were the largest at large wave height. The three-cylinder floating breakwater exhibited satisfactory hydrodynamic performance under the influence of reefs. It has broad application prospects in offshore reefs. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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27 pages, 5429 KiB  
Article
Design and Analysis of a Mooring System for a Wave Energy Converter
by Francesco Depalo, Shan Wang, Sheng Xu and C. Guedes Soares
J. Mar. Sci. Eng. 2021, 9(7), 782; https://doi.org/10.3390/jmse9070782 - 19 Jul 2021
Cited by 13 | Viewed by 5527
Abstract
The objective of this work is to develop an efficient method to carry out the preliminary design of the mooring system for a wave energy converter. A practical mooring design procedure is applied to a specific case of study, and it can be [...] Read more.
The objective of this work is to develop an efficient method to carry out the preliminary design of the mooring system for a wave energy converter. A practical mooring design procedure is applied to a specific case of study, and it can be replicated for other cases. Firstly, the static analysis is performed for a configuration with three mooring cables with different pre-tensions on fairlead, diameters of the cables, and materials. Based on these configurations from the static analysis, a quasi-static analysis is carried out in the frequency domain and a preliminary design is conducted according to DNV rules. Then, a 3-h dynamic analysis in the time domain is performed on several selected configurations, considering the same environmental conditions in the quasi-static analysis using the finite element method. Extreme dynamic responses of the system, such as extreme surge motion and mooring tensions, are estimated by the global maximum method, which is performed by fitting 20 individual maximum observations by Gumbel distribution. The quasi-static method is validated by comparing the results of extreme tension and displacement with the coupled time domain analysis. In addition, the influence of pre-tensions and cable diameters on the static and dynamic responses of the mooring system are discussed. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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