Special Issue "Mooring of Floating Offshore 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 (31 December 2021) | Viewed by 5902

Special Issue Editors

Dr. Thomas E. Schellin
E-Mail Website
Guest Editor
Institute of Ship Technology and Ocean Engineering, University of Duisburg-Essen, 47057 Duisburg, Germany
Interests: offshore structures; fluid-structure interaction
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Bettar Ould el Moctar
E-Mail Website
Guest Editor
Department Mechanical and Process Engineering, Faculty of Engineering, University of Duisburg-Essen, Bismarkstrasse 69, 47057 Duisburg, Germany
Interests: fluid dynamics; offshore structures; fluid-structure interaction
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Over the past several decades, there has been a continuous stream of innovations in ocean-based structures and systems applied not only in the oil and gas area, but also more recently in the floating offshore wind energy, wave energy, and seafloor mineral harvesting sectors. Furthermore, owing to the scarcity of land, very large floating structures are now being designed to cater to an increasing population in coastal areas. All of these structures must maintain station; that is, their mooring systems must withstand the forces of the ocean over long asset lives in the corrosive sea–air interface, while operating under various environmental conditions. It is equally important to understand overall construction processes, while considering environmental issues and regulatory frameworks. In addition, significant cost reductions are required in order for floating structures to become competitive, and one key area that has the potential for cost reduction is the mooring system. This Special Issue aims to provide a forum supporting the development of innovative and effective moorings of floating offshore structures.

Dr. Thomas E. Schellin
Prof. Dr. Bettar Ould el Moctar
Guest Editors

Manuscript Submission Information

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Keywords

  • Mooring
  • Offshore structures
  • Wind energy
  • Wave energy
  • Very large floating structures
  • Wave loads
  • CFD

Published Papers (6 papers)

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Research

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Article
Effect of Various Mooring Materials on Hydrodynamic Responses of Turret-Moored FPSO with Emphasis on Intact and Damaged Conditions
J. Mar. Sci. Eng. 2022, 10(4), 453; https://doi.org/10.3390/jmse10040453 - 23 Mar 2022
Viewed by 515
Abstract
The behavior of different mooring line materials has a significant influence on the behavior of the mooring system and, consequently, the dynamic responses of the floating platform. Although there have been previous studies on FPSOs and their mooring systems, the influence of mooring [...] Read more.
The behavior of different mooring line materials has a significant influence on the behavior of the mooring system and, consequently, the dynamic responses of the floating platform. Although there have been previous studies on FPSOs and their mooring systems, the influence of mooring line failure scenarios associated with different mooring materials has received less attention, particularly for turret-moored FPSOs with taut moorings. Thus, this paper investigates the behavior of different mooring line materials in intact, single-line, and double-line damaged conditions on the hydrodynamic responses of the FPSO, restoring behavior, mooring, and riser tensions considering wave conditions in the Gulf of Mexico. Mooring lines including Aramid, HMPE, polyester, and steel wire were considered in the middle segment, which was the segment of interest in this study. The restoring forces of the mooring system were found to increase with increasing mooring stiffness, and a higher stiffness resulted in a higher loss of restoring force in the case of single-line failure. In all cases, the submerged weight and material stiffness had a significant influence on dynamic responses, mooring tension, transient responses, riser tension, and especially on the ability of the mooring system to resist the case of single-line failure. Each material was observed to behave differently in each degree of freedom (DOF), showing the necessity to pay close attention to the selection of mooring material for specific objectives. Full article
(This article belongs to the Special Issue Mooring of Floating Offshore Structures)
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Article
Hydrodynamic Sensitivity of Moored and Articulated Multibody Offshore Structures in Waves
J. Mar. Sci. Eng. 2021, 9(9), 1028; https://doi.org/10.3390/jmse9091028 - 18 Sep 2021
Viewed by 647
Abstract
Within the framework of [email protected] project, an articulated modular floating structure was developed to serve as building blocks for artificial islands. The modularity was one of the key elements, intended to provide the desired flexibility of additional deck space at sea. Consequently, the [...] Read more.
Within the framework of [email protected] project, an articulated modular floating structure was developed to serve as building blocks for artificial islands. The modularity was one of the key elements, intended to provide the desired flexibility of additional deck space at sea. Consequently, the layout of a modular floating concept may change, depending on its functionality and environmental condition. Employing a potential-flow-based numerical model (i.e., weakly nonlinear Green function solver AQWA), this paper studied the hydrodynamic sensitivity of such multibody structures to the number of modules, to the arrangement of these modules, and to the incident wave angle. Results showed that for most wave frequencies, their hydrodynamic characteristics were similar although the floating platforms consisted of a different number of modules. Only translational horizontal motions, i.e., surge and sway, were sensitive to the incident wave angle. The most critical phenomenon occurred at head seas, where waves traveled perpendicularly to the rotation axes of hinged joints, and the hinge forces were largest. Hydrodynamic characteristics of modules attached behind the forth module hardly changed. The highest mooring line tensions arose at low wave frequencies, and they were caused by second-order mean drift forces. First-order forces acting on the mooring lines were relatively small. Apart from the motion responses and mooring tensions, forces acting on the hinge joints governed the system’s design. The associated results contribute to design of optimal configurations of moored and articulated multibody floating islands. Full article
(This article belongs to the Special Issue Mooring of Floating Offshore Structures)
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Article
Mooring-Configurations Induced Decay Motions of a Buoy
J. Mar. Sci. Eng. 2021, 9(3), 350; https://doi.org/10.3390/jmse9030350 - 23 Mar 2021
Viewed by 953
Abstract
The hydrodynamic damping of a buoy stationed with three different mooring configurations was estimated using a Navier-Stokes (NS) equations solver coupled with a dynamic mooring model. The mooring configurations comprised a catenary system, a catenary system with sub floaters, and a catenary system [...] Read more.
The hydrodynamic damping of a buoy stationed with three different mooring configurations was estimated using a Navier-Stokes (NS) equations solver coupled with a dynamic mooring model. The mooring configurations comprised a catenary system, a catenary system with sub floaters, and a catenary system with sub floaters and clump weights. Systematic simulations were achieved by adopting the overset grid scheme instead of the conventional morphing grid scheme, which required regenerating the entire mesh when the buoy’s initial position changed, thereby avoiding mesh distortions and numerical instabilities. Motion decay simulations in heave, pitch, and surge were conducted with and without various mooring systems. The analyzed results comprised decaying oscillating motions, natural periods, and associated amounts of damping. The mooring systems influenced not only restoring force characteristics, but also total damping of the moored buoy, which demonstrated the importance of considering mooring-induced damping when investigating moored offshore structures. Full article
(This article belongs to the Special Issue Mooring of Floating Offshore Structures)
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Article
A Study on the Effectiveness of the Heading Control on the Mooring Line Tension and Position Offset for an Arctic Floating Structure under Complex Environmental Loads
J. Mar. Sci. Eng. 2021, 9(2), 102; https://doi.org/10.3390/jmse9020102 - 20 Jan 2021
Cited by 1 | Viewed by 684
Abstract
Even though interest in developing the Arctic region is increasing continuously, the standard procedure to be used to analyze the station-keeping performance of a floater considering ice loads has not been established yet. In this paper, the effectiveness of heading control with a [...] Read more.
Even though interest in developing the Arctic region is increasing continuously, the standard procedure to be used to analyze the station-keeping performance of a floater considering ice loads has not been established yet. In this paper, the effectiveness of heading control with a dynamic positioning system is analyzed to evaluate the improvement of the performance of the station-keeping system in the ice conditions. Complex environmental loads with ice-induced forces were generated and applied to a ship type floater with dynamic positioning and mooring systems. Three-hour time-domain simulations were conducted for the two different station-keeping systems with mooring only and mooring with a dynamic positioning system. Position offsets and mooring line tensions for the two scenarios were compared with maximum values and most probable maxima (MPM) values. The results of the simulation showed that the heading control can reduce 8.2% of MPM values for the mooring lines and improve the station-keeping performance by about 16.3%. The validity of the station-keeping system that was designed was confirmed, and it is expected that the specification of mooring lines can be relaxed with the heading control. Full article
(This article belongs to the Special Issue Mooring of Floating Offshore Structures)
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Article
A Simplified Numerical Method for the Design and Analysis of FPSO Platform Brackets Subjected to Operational Conditions
J. Mar. Sci. Eng. 2020, 8(11), 929; https://doi.org/10.3390/jmse8110929 - 16 Nov 2020
Cited by 1 | Viewed by 835
Abstract
The present work develops a simplified computational methodology to predict brackets’ mechanical behavior to support mooring systems’ fairleads under maximum environmental loads. The methodology consists of estimating environmental loads in Campos’s basin (Brazil) using standards available in the literature and applying them to [...] Read more.
The present work develops a simplified computational methodology to predict brackets’ mechanical behavior to support mooring systems’ fairleads under maximum environmental loads. The methodology consists of estimating environmental loads in Campos’s basin (Brazil) using standards available in the literature and applying them to determine the stress distribution in the brackets’ solid domain using a code based on the Finite Element Method. The brackets studied here are composed of AH36 steel plates. Six different geometric configurations for the brackets considering thinner plates than those ordinarily employed in the existent brackets of the P-66 Petrobras oil production platform were studied. Theoretical recommendations about geometric configurations to reduce the von Mises maximum stress in brackets’ plates were determined in the light of constructal design. The results proved the importance of the geometric investigation in this problem. For instance, for the accidental limit state (ALS) the best configuration leads to a mechanical performance two times superior to that reached for the worst one, which had a maximum stress superior to the yielding limit. Moreover, the best designs for the superior and inferior brackets in the ALS have different configurations. Full article
(This article belongs to the Special Issue Mooring of Floating Offshore Structures)
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Review

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Review
An Overview on Bonded Marine Hoses for Sustainable Fluid Transfer and (Un)Loading Operations via Floating Offshore Structures (FOS)
J. Mar. Sci. Eng. 2021, 9(11), 1236; https://doi.org/10.3390/jmse9111236 - 08 Nov 2021
Cited by 17 | Viewed by 1023
Abstract
Due to the demand for oil production in varying water depth regions, the advantage of flexible buoyant conduits has led to an increase in bonded marine hoses for fluid transfer and (un)loading operations. The fluid transfer system for bonded marine hoses is dependent [...] Read more.
Due to the demand for oil production in varying water depth regions, the advantage of flexible buoyant conduits has led to an increase in bonded marine hoses for fluid transfer and (un)loading operations. The fluid transfer system for bonded marine hoses is dependent on floating offshore structures (FOS). This paper presents an overview of different systems for sustainable fluid transfer and (un)loading operations via FOS, such as Single Point Mooring (SPM) systems. SPMs are component aspects of the techno-economic design and FOS operation. This review aims to present sustainable fluid transfer technologies while addressing the subject of bonded marine hoses based on application, configuration, test models, hose selection criteria, hose-mooring configurations and operational views. This paper also includes an overview of the hose dynamics, with the loading and unloading (or discharging) techniques for sustainable fluid transfer via marine bonded hoses, based on operational challenges encountered. To dynamically present the hose performance in this review, an overview of the test methods’ guidance as specified in available industry standards was conducted. The pros and cons of marine hose application were also presented. Finally, this study presents different marine hose types and novel design configurations applied in implementing hose-mooring systems. Some concluding remarks with recommended solutions on the technology were presented in this review. Full article
(This article belongs to the Special Issue Mooring of Floating Offshore Structures)
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