Advances in Position Mooring

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 (15 March 2021) | Viewed by 13639

Special Issue Editors


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Guest Editor
Departments of Mechanics and Maritime Sciences and Architecture and Civil Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
Interests: computational fluid dynamics applied to hydraulics and environmental problems, e.g., mixing in ponds and reservoirs, flow over weirs, and flow in rivers, the dynamics and fatigue of mooring cables, and wave energy studies; water surface gravity waves, especially wave forces on and wave-induced motions of fixed and floating structures

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Guest Editor
Department of the Built Environment, Aalborg University, Thomas Manns Vej 23, DK-9220 Aalborg Ø, Denmark
Interests: numerical modelling; wave propagation; wave–body interaction; wave energy; mooring; high-order finite element models; computational fluid dynamics
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Guest Editor
Development and Research in Environment, Applied Management and Space, Universidade Lusófona do Porto, Rua Augusto Rosa, nº 24, 4000-098 Porto, Portugal
Interests: mooring systems; wave energy; floating wind turbines; physical and numerical modelling; time and frequency domain analysis; uncertainty quantification
Department of Mechanics and Maritime Sciences, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
Interests: mooring dynamics; wave energy; computational fluid dynamics; finite element methods

Special Issue Information

Dear Colleagues,

Position mooring is a fundamental topic in ocean and marine engineering as it aims to assure safe operation of floating structures. However, the reported failure rates of mooring cables for oil and gas (O&G) installations are surprisingly high. While the O&G sector handles this with redundancy in the design, the marine renewable sector cannot cover that expenditure. Our knowledge of mooring needs to be improved to increase reliability and reduce operation and maintenance (O&M) costs. It also needs to address the new challenges posed by the requirements of floating renewable energy devices, such as station-keeping of devices in large parks with reduced seabed footprints and detrimental effects in floater dynamics.

For this Special Issue, we would like to invite the submission of papers dealing with position mooring in a broad sense. This includes both experimental and numerical investigations on physical phenomena (e.g., snapping and strumming), fatigue monitoring, and condition monitoring. We are especially interested in work that aims to reduce the uncertainties associated with mooring dynamics, such as ground interactions, cable material modelling, and internal damping effects. Additionally, papers presenting innovative solutions to mooring design problems—including designs for newly emerging fields, such as floating solar parks, offshore aqua-culture, and mega-islands—are highly encouraged.

Prof. Em. Lars Bergdahl
Assoc. Prof. Claes Eskilsson
Dr. Guilherme Moura Paredes
Dr. Johannes Palm
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

  • station-keeping
  • experimental and numerical investigations of mooring systems
  • snap loads and strumming
  • ground interaction
  • mooring-induced damping
  • reliability analysis and reliability-based design
  • condition monitoring
  • survival
  • innovative mooring designs and applications

Published Papers (4 papers)

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Research

23 pages, 1496 KiB  
Article
A Numerical Solution for Modelling Mooring Dynamics, Including Bending and Shearing Effects, Using a Geometrically Exact Beam Model
by Tobias Martin and Hans Bihs
J. Mar. Sci. Eng. 2021, 9(5), 486; https://doi.org/10.3390/jmse9050486 - 30 Apr 2021
Cited by 10 | Viewed by 2718
Abstract
During the operation of moored, floating devices in the renewable energy sector, the tight coupling between the mooring system and floater motion results in snap load conditions. Before snap events occur, the mooring line is typically slack. Here, the mechanism of energy propagation [...] Read more.
During the operation of moored, floating devices in the renewable energy sector, the tight coupling between the mooring system and floater motion results in snap load conditions. Before snap events occur, the mooring line is typically slack. Here, the mechanism of energy propagation changes from axial to bending dominant, and the correct modelling of the rotational deformation of the lines becomes important. In this paper, a new numerical solution for modelling the mooring dynamics that includes bending and shearing effects is proposed for this purpose. The approach is based on a geometrically exact beam model and quaternion representations for the rotational deformations. Further, the model is coupled to a two-phase numerical wave tank to simulate the motion of a moored, floating offshore wind platform in waves. A good agreement between the proposed numerical model and reference solutions was found. The influence of the bending stiffness on the motion of the structure was studied subsequently. We found that increased stiffness increased the amplitudes of the heave and surge motion, whereas the motion frequencies were less altered. Full article
(This article belongs to the Special Issue Advances in Position Mooring)
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20 pages, 1340 KiB  
Article
Numerical Modelling for Synthetic Fibre Mooring Lines Taking Elongation and Contraction into Account
by Ivan Ćatipović, Neven Alujević, Smiljko Rudan and Vedran Slapničar
J. Mar. Sci. Eng. 2021, 9(4), 417; https://doi.org/10.3390/jmse9040417 - 13 Apr 2021
Cited by 5 | Viewed by 2339
Abstract
Synthetic fibre mooring lines are used as an alternative to traditional steel wire ropes due to their higher strength to weight ratio. Benefits are also found in relative ease of handling, and therefore the marine industry has largely accepted this type of mooring [...] Read more.
Synthetic fibre mooring lines are used as an alternative to traditional steel wire ropes due to their higher strength to weight ratio. Benefits are also found in relative ease of handling, and therefore the marine industry has largely accepted this type of mooring line. By rules and regulations, the design of mooring lines should be based on a coupled dynamic analysis of a particular mooring system and moored vessel. This approach incorporates damping and inertial forces (i.e., hydrodynamic reactions) acting directly on the mooring lines due to their motion through the seawater. On the basis of the outer diameter of the synthetic fibre rope, the Morison equation gives estimations of the mooring line hydrodynamic reactions. In comparison to the traditional steel wire ropes, the synthetic mooring lines usually have relatively larger elongations and consequently larger reductions of the outer diameter. Furthermore, the lower diameter certainly leads to reduced values of damping and added mass (of mooring lines) that should be considered in the coupled model. Therefore, the aim of this study was to develop a new numerical model that includes diameter changes and axial deformations when estimating the hydrodynamic reactions. The development of the model is carried out with a nonlinear finite element method for mooring lines with the assumption of large three-dimensional motions. The obtained results show the effectiveness of the newly developed model as a more accurate approach in calculation of hydrodynamic reactions. Full article
(This article belongs to the Special Issue Advances in Position Mooring)
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20 pages, 2988 KiB  
Article
Influence of Bending Stiffness on Snap Loads in Marine Cables: A Study Using a High-Order Discontinuous Galerkin Method
by Johannes Palm and Claes Eskilsson
J. Mar. Sci. Eng. 2020, 8(10), 795; https://doi.org/10.3390/jmse8100795 - 13 Oct 2020
Cited by 14 | Viewed by 2081
Abstract
Marine cables are primarily designed to support axial loads. The effect of bending stiffness on the cable response is therefore often neglected in numerical analysis. However, in low-tension applications such as umbilical modelling of ROVs or during slack events, the bending forces may [...] Read more.
Marine cables are primarily designed to support axial loads. The effect of bending stiffness on the cable response is therefore often neglected in numerical analysis. However, in low-tension applications such as umbilical modelling of ROVs or during slack events, the bending forces may affect the slack regime dynamics of the cable. In this paper, we present the implementation of bending stiffness as a rotation-free, nested local Discontinuous Galerkin (DG) method into an existing Lax–Friedrichs-type solver for cable dynamics based on an hp-adaptive DG method. Numerical verification shows exponential convergence of order P and P+1 for odd and even polynomial orders, respectively. Validation of a swinging cable shows good comparison with experimental data, and the importance of bending stiffness is demonstrated. Snap load events in a deep water tether are compared with field-test data. The bending forces affect the low-tension response for shorter lengths of tether (200–500 m), which results in an increasing snap load magnitude for increasing bending stiffness. It is shown that the nested LDG method works well for computing bending effects in marine cables. Full article
(This article belongs to the Special Issue Advances in Position Mooring)
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15 pages, 1884 KiB  
Article
Parametric Study of a Taut Compliant Mooring System for a FOWT Compared to a Catenary Mooring
by Magnus Thorsen Bach-Gansmo, Stian Kielland Garvik, Jonas Bjerg Thomsen and Morten Thøtt Andersen
J. Mar. Sci. Eng. 2020, 8(6), 431; https://doi.org/10.3390/jmse8060431 - 12 Jun 2020
Cited by 12 | Viewed by 5615
Abstract
The catenary mooring system is a well recognized station keeping method. However, there could be economical and environmental benefits of reducing the footprint. In the last decades, more focus has been given to synthetic mooring lines and different mooring layouts to optimize the [...] Read more.
The catenary mooring system is a well recognized station keeping method. However, there could be economical and environmental benefits of reducing the footprint. In the last decades, more focus has been given to synthetic mooring lines and different mooring layouts to optimize the levelized cost of energy (LCOE) for offshore renevable energy converters such as wave energy converters. Therefore, this work presents a parametric study of two important parameters, namely the mooring line angle and line pretension, for a taut mooring configuration focusing on the dynamic response when applied to the TetraSpar floating foundation compared to a catenary mooring system. The work is based on experimental results conducted in the wave basin at Aalborg University (AAU) and compared to analytical stiffness calculations. In addition, a numerical model was tuned based on the main dynamics to achieve the tension response. The results showed satisfying dynamic behavior where the angle and pretension mainly influenced the surge and yaw natural periods. The motion response showed similar behavior between the chosen parameters, and larger pitch amplitudes were found compared to the catenary system. Full article
(This article belongs to the Special Issue Advances in Position Mooring)
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