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Publications (10 of 59) Show all publications
Kuznecovs, A., Ringsberg, J., Yang, S. H., Johnson, E. & Anderson, A. (2019). A methodology for design and fatigue analysis of power cables for wave energy converters. International Journal of Fatigue, 122, 61-71
Open this publication in new window or tab >>A methodology for design and fatigue analysis of power cables for wave energy converters
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2019 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 122, p. 61-71Article in journal (Refereed) Published
Abstract [en]

The recent development of subsea power cables for various offshore marine renewable energy technologies has identified the need for new cables that have low structural stiffness properties. This type of cable is referred to as dynamic cable because of its high bending flexibility compared to static cables. The current study presents a cable design model and simulation models that were developed for the design and fatigue analysis of dynamic cables. These models were applied on a subsea dynamic power cable with a design that is suitable for a floating point-absorbing wave energy converter (WEC), where the cable must withstand cyclic loads imposed by the motions of the WEC, the waves and the ocean currents. The cable design model is presented with its detailed design and dimensioning methodology for cables with multiorder helical structures, with respect to desired (target) mechanical properties. The cable design model is verified against a verification study in the literature. A simulation model of a fatigue test rig for accelerated rotational bending is presented. The results from the numerical simulations and the subsequent fatigue analyses are compared against results from experiments using the test rig. The influence of the dynamic effects and mechanical properties on the fatigue life of the cable is discussed. This study contributes to a better understanding of the fatigue failure mechanisms of the cable, and it also highlights the importance of further development of numerical models.

Keywords
Cable design, Dynamic cables, Fatigue, Power cables, Wave energy converter
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-37693 (URN)10.1016/j.ijfatigue.2019.01.011 (DOI)2-s2.0-85060328030 (Scopus ID)
Note

 Funding details: Energimyndigheten, 41240-1; Funding details: Chalmers Tekniska Högskola; Funding text 1: Chalmers University of Technology and The Swedish Energy Agency are acknowledged for their financial support to this study through the project “R&D of dynamic low voltage cables between the buoy and floating hub in a marine energy system” (project number 41240-1).

Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2019-02-01Bibliographically approved
Sanchez, L., Ringsberg, J. & Johnson, E. (2019). Effective use of composite marine structures: Reducing weight and acquisition cost: Chapter 6. In: Richard Pemberton, John Summerscales and Jasper Graham-Jones (Ed.), Marine Composites : Design and Performance  (A volume in Woodhead Publishing Series in Composites Science and Engineering): (pp. 161-183).
Open this publication in new window or tab >>Effective use of composite marine structures: Reducing weight and acquisition cost: Chapter 6
2019 (English)In: Marine Composites : Design and Performance  (A volume in Woodhead Publishing Series in Composites Science and Engineering) / [ed] Richard Pemberton, John Summerscales and Jasper Graham-Jones, 2019, p. 161-183Chapter in book (Other academic)
Abstract [en]

Composite structures are a way to reduce the operational costs of a vessel or to increase its potential revenue. However, depending on the design of the vessel, its operational profile, and the business model of the owner, the benefits brought by a composite structure may not justify its acquisition cost. This paper presents a number of investigations aimed at reducing the acquisition cost of marine composite structures and maximizing their benefits through a more effective use of composite materials (in other words, weight reduction of the composite structure). The investigations cover three areas of opportunity for doing so: material safety factors, material characterization, and numerical optimization of large composite structures. The following conclusions are drawn from the investigations: motivating a reduction of material safety factors through probabilistic analyses is unpractical at best, and questionable at worst; improving the material characterization of textile composites is easy, relatively costless, and can modestly reduce structural weight through better material property values; numerical optimization of large composite structures is cumbersome, but feasible, and holds the greatest potential increasing the economical attractiveness of composite marine structures.

National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36338 (URN)10.1016/C2016-0-00710-6 (DOI)9780081022641 (ISBN)
Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2018-11-21Bibliographically approved
Ringsberg, J., Li, Z., Kuznecovs, A. & Johnson, E. (2018). Analysis of theultimate strength of corroded ships involved in collision accidents andsubjected to biaxial bending. In: : . Paper presented at Fourth International Conference on Maritime Technology and Engineering (MARTECH 2018) in Lisbon, Portugal, May 7-9, 2018. (pp. 327-336).
Open this publication in new window or tab >>Analysis of theultimate strength of corroded ships involved in collision accidents andsubjected to biaxial bending
2018 (English)Conference paper, Published paper (Other academic)
Abstract [en]

This study presents an analysis of the effects of sudden damage, and progressive deterioration due to corrosion, on the ultimate strength of a ship which has been collided by another vessel. Finite element analyses (FEA) of collision scenarios are presented where factors are varied e.g. the vessels involved in the collision, and consider-ation of corroded ship structure elements and their material characteristics in the model. The striking ship is a coastal tanker, the struck ship is either a RoPax ship, or, a coastal oil tanker vessel. The ultimate strength analy-sis of the struck vessel accounts for the shape and size of the damage opening from the FEA. The Smith method is used to calculate the ultimate strength of intact and damaged ship structures during biaxial bending. The study shows how corroded, collision-damaged ship structures suffer from a reduction in crashworthiness and ultimate strength, how this should be considered and modelled in FEA.

National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36343 (URN)10.1201/9780429505294-38 (DOI)2-s2.0-85061348889 (Scopus ID)9781138585393 (ISBN)
Conference
Fourth International Conference on Maritime Technology and Engineering (MARTECH 2018) in Lisbon, Portugal, May 7-9, 2018.
Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2019-03-19Bibliographically approved
Yang, S., Ringsberg, J. & Johnson, E. (2018). Analysis ofinteraction effects between WECs in four types of wave farms.. In: Advances in Renewable Energies Offshore - Proceedings of The 3rdInternational Conference on Renewable Energies Offshore (RENEW 2018),: . Paper presented at 3rd International Conference on Renewable Energies Offshore (RENEW 2018), Lisbon, Portugal, October 8-10, 2018. (pp. 647-658).
Open this publication in new window or tab >>Analysis ofinteraction effects between WECs in four types of wave farms.
2018 (English)In: Advances in Renewable Energies Offshore - Proceedings of The 3rdInternational Conference on Renewable Energies Offshore (RENEW 2018),, 2018, p. 647-658Conference paper, Published paper (Refereed)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36346 (URN)9781138585355 (ISBN)
Conference
3rd International Conference on Renewable Energies Offshore (RENEW 2018), Lisbon, Portugal, October 8-10, 2018.
Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2018-11-21Bibliographically approved
Lang, X., Yang, S., Ringsberg, J., Johnson, E., Rahm, M. & Guedes Soares, C. (2018). Comparison betweenfull-scale measurements and numerical simulations of mooring forces in afloating point-absorbing WEC system.. In: Advances in Renewable Energies Offshore - Proceedings of The 3rdInternational Conference on Renewable Energies Offshore (RENEW 2018),: . Paper presented at The 3rd International Conference on Renewable Energies Offshore (RENEW 2018), Lisbon, Portugal, October 8-10, 2018. (pp. 865-876).
Open this publication in new window or tab >>Comparison betweenfull-scale measurements and numerical simulations of mooring forces in afloating point-absorbing WEC system.
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2018 (English)In: Advances in Renewable Energies Offshore - Proceedings of The 3rdInternational Conference on Renewable Energies Offshore (RENEW 2018),, 2018, p. 865-876Conference paper, Published paper (Refereed)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36345 (URN)9781138585355 (ISBN)
Conference
The 3rd International Conference on Renewable Energies Offshore (RENEW 2018), Lisbon, Portugal, October 8-10, 2018.
Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2018-11-21Bibliographically approved
Ringsberg, J., Jansson, H., Yang, S. H., Örgård, M. & Johnson, E. (2018). Comparison of mooring solutions and array systems for point absorbing wave energy devices. In: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE: . Paper presented at ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2018, 17 June 2018 through 22 June 2018. Madrid, Spain..
Open this publication in new window or tab >>Comparison of mooring solutions and array systems for point absorbing wave energy devices
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2018 (English)In: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Most of the ocean energy technologies are considered to be ina pre-commercial phase and need technical development. Thisstudy focuses on design of mooring solutions and comparesarray systems of a specific floating point-absorbing waveenergy converter (WEC) developed by the companyWaves4Power. A full-scale prototype of the WEC is installedin Runde (Norway) where it is moored with three polyestermooring lines, each having one floater and one gravity anchor.Based on this reference installation, the method of systemsengineering was used to propose twenty-two conceptualmooring solutions for different array systems. They werecompared and reduced to four top concepts in a systematicelimination procedure using Pugh and Kesselring matrices. Thetop concepts were assessed in detail by means of LCOE(levelised cost of energy), LCA (life cycle analysis) and riskanalyses. The fatigue life of the mooring lines and the energycapture were calculated using results obtained from coupledhydrodynamic and structure response analyses in the DNV-GLDeepC software. Two final concepts were proposed for thewater depths 75 and 200 m.

Keywords
Array system, Coupled analysis, Mooring solution, Systems engineering, Wave energy, Digital arithmetic, Life cycle, Mooring, Mooring cables, Ocean engineering, Oceanography, Offshore oil well production, Wave energy conversion, Array systems, Floating points, Levelised cost of energies, Life cycle analysis, Structure response, Technical development, Arctic engineering
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-35923 (URN)10.1115/OMAE2018-77062 (DOI)2-s2.0-85055452499 (Scopus ID)9780791851326 (ISBN)
Conference
ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2018, 17 June 2018 through 22 June 2018. Madrid, Spain.
Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-19Bibliographically approved
Yang, S.-H., Ringsberg, J. W., Johnson, E., Hu, Z., Bergdahl, L. & Duan, F. (2018). Experimental and numerical investigation of a taut-moored wave energy converter: A validation of simulated buoy motions. Journal of Engineering for the Maritime Environment (Part M), 232(1), 97-115
Open this publication in new window or tab >>Experimental and numerical investigation of a taut-moored wave energy converter: A validation of simulated buoy motions
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2018 (English)In: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, E-ISSN 2041-3084, Vol. 232, no 1, p. 97-115Article in journal (Refereed) Published
Abstract [en]

This study presents an experimental and numerical investigation of a taut-moored wave energy converter system with a point-absorber type of wave energy converter. The wave energy converter system consists of a buoy, a unique three-leg two-segment mooring system with submerged floaters, and a power take-off system designed for the current experiment as a heave plate. The main objective of the study is to validate a numerical simulation model against experiments carried out in an ocean basin laboratory. Two physical models in model scales 1:20 and 1:36 were built and tested. The detailed experimental testing programme encompasses tests of mooring system stiffness, decay tests, and different sea state conditions for ocean current, regular, and irregular waves. A numerical model in the model scale 1:20 was developed to simulate coupled hydrodynamic and structural response analyses of the wave energy converter system, primarily using potential flow theory, boundary element method, finite element method, and the Morison equation. Several numerical simulations are presented for each part of the experimental testing programme. Results for the wave energy converter buoy motions under operational conditions from the experiments and the numerical simulations were compared. This study shows that the simulation model can satisfactorily predict the dynamic motion responses of the wave energy converter system at non-resonant conditions, while at resonant conditions additional calibration is needed to capture the damping present during the experiment. A discussion on simulation model calibration with regard to linear and non-linear damping highlights the challenge to estimate these damping values if measurement data are not available.

Keywords
Experiment, model validation, point absorber, simulation, taut mooring, wave energy converter, Boundary element method, Buoyancy, Buoys, Damping, Experiments, Finite element method, Mooring, Numerical methods, Numerical models, Ocean currents, Power takeoffs, Sailing vessels, Verification, Wave power, Numerical investigations, Operational conditions, Power take-off systems, Structural response analysis, Wave energy converters, Wave energy conversion
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33452 (URN)10.1177/1475090217735954 (DOI)2-s2.0-85042281525 (Scopus ID)
Note

 Funding details: P36357-2, Energimyndigheten/Swedish Energy Agency

Available from: 2018-03-09 Created: 2018-03-09 Last updated: 2019-02-01Bibliographically approved
Ringsberg, J. W., Li, Z., Johnson, E., Kuznecovs, A. & Shafieisabet, R. (2018). Reduction in ultimate strength capacity of corroded ships involved in collision accidents. Ships and Offshore Structures, 13, 155-166
Open this publication in new window or tab >>Reduction in ultimate strength capacity of corroded ships involved in collision accidents
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2018 (English)In: Ships and Offshore Structures, ISSN 1744-5302, E-ISSN 1754-212X, Vol. 13, p. 155-166Article in journal (Refereed) Published
Abstract [en]

The objective of the study is to investigate the effects of sudden damage, and progressive deterioration due to corrosion, on the ultimate strength of a ship which has been collided by another vessel. Explicit finite element analyses (FEA) of collision scenarios are presented where factors are varied systematically in a parametric study, e.g. the vessels involved in the collision, and consideration of corroded ship structure elements and their material characteristics in the model. The crashworthiness of the struck ships is quantified in terms of the shape and size of the damage opening in the side-shell structure, and the division of energy absorption between the striking and struck ships for the different collision simulations. The ultimate strength of the struck ship is calculated using the Smith method and the shape and size of the damage openings from the FEA. In conclusion, the study contributes to understanding of how corroded, collision-damaged ship structures suffer significantly from a reduction in crashworthiness and ultimate strength, how this should be considered and modelled using the finite element method and analysed further using the Smith method.

Keywords
Corrosion, parametric study, ship–ship collision, Smith method, ultimate strength, Crashworthiness, Mechanical variables measurement, Ships, Collision accidents, Explicit finite element analysis, Material characteristics, Ship collision, Ultimate strength capacity, Finite element method
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33462 (URN)10.1080/17445302.2018.1429158 (DOI)2-s2.0-85041204946 (Scopus ID)
Available from: 2018-03-09 Created: 2018-03-09 Last updated: 2018-11-19Bibliographically approved
Erikson, M. G., Eriksson, A., Johnson, E., Nagy, A. & Richards, T. (2017). A conceptual model of how research can influence student development. In: Connecting Higher Education International perspectives on research-based education BOOK OF ABSTRACTS. Tues 27 June to Wed 28 June 2017. London, United Kingdom: . Paper presented at Connecting Higher Education International perspectives on research-based education. Tues 27 June to Wed 28 June 2017. London, United Kingdom (pp. 71-72). , Article ID 86.
Open this publication in new window or tab >>A conceptual model of how research can influence student development
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2017 (English)In: Connecting Higher Education International perspectives on research-based education BOOK OF ABSTRACTS. Tues 27 June to Wed 28 June 2017. London, United Kingdom, 2017, p. 71-72, article id 86Conference paper, Oral presentation with published abstract (Refereed)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33275 (URN)
Conference
Connecting Higher Education International perspectives on research-based education. Tues 27 June to Wed 28 June 2017. London, United Kingdom
Available from: 2018-02-16 Created: 2018-02-16 Last updated: 2019-01-07Bibliographically approved
Yang, S.-H., Ringsberg, J., Johnson, E. & Hu, Z. (2017). Biofouling on mooring lines and power cables used in wave energy converter systems - analysis of fatigue life and energy performance. Applied Ocean Research, 65, 166-177
Open this publication in new window or tab >>Biofouling on mooring lines and power cables used in wave energy converter systems - analysis of fatigue life and energy performance
2017 (English)In: Applied Ocean Research, ISSN 0141-1187, E-ISSN 1879-1549, Vol. 65, p. 166-177Article in journal (Refereed) Published
Abstract [en]

This study presents an analysis of a wave energy converter (WEC) system consisting of a buoy, a mooring system, and a power cable connected to a hub. The investigated WEC system is currently under full-scale testing near Runde in Norway. The purpose of the study was to investigate the characteristics of the entire system, primarily with regard to energy performance and the fatigue life of the mooring lines and power cable, considering the effects of marine biofouling and its growth on the system’s components. By means of parametric study, the energy performance and fatigue life of the mooring lines and power cable were investigated considering two mooring configurations, three biofouling conditions, four sea states in a scatter diagram, and three wave and current directions. Hydrodynamic and structural response simulations were conducted in a coupled response analysis using the DNV-GL software SESAM. Energy performance analyses and stress-based rainflow counting fatigue calculations were performed separately using an in-house code. The results show that, for a WEC system which has been deployed for 25 years, biofouling can reduce the total power absorption by up to 10% and decrease the fatigue life of the mooring lines by approximately 20%

Keywords
Biofouling; Catenary mooring chain; Fatigue; Power absorption; Power cable; Wave energy converter
National Category
Vehicle Engineering Materials Engineering
Identifiers
urn:nbn:se:ri:diva-30015 (URN)10.1016/j.apor.2017.04.002 (DOI)2-s2.0-85018515620 (Scopus ID)
Available from: 2017-06-29 Created: 2017-06-29 Last updated: 2019-01-07Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7182-0872

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