Numerical model validation for mooring systems: Method and application for wave energy converters

PublishedArticleMooring systems are key sub-systems of wave energy devices. The design of mooring systems is challenging because overdesign of the mooring system incurs a significant cost penalty, while underdesign may lead to a premature failure. Incorrect design could also reduce the power production. It is therefore important to develop mooring systems which are specific for wave energy applications. In particular, very compliant mooring systems which allow the system to be highly dynamic are being developed. The validation of numerical models with data from physical experiments would facilitate the development of appropriate mooring solutions. This paper presents tank test results for a scale model of the buoy and mooring used at the South West Mooring Test Facility (SWMTF), an offshore facility developed to conduct long-term sea trials for wave energy device moorings. The mooring system investigated is a compliant 3 leg catenary mooring system using Nylon ropes in the water column. Preliminary static, quasi-static, decay, regular and irregular wave tests were conducted on the 1:5 scale model, using the Ifremer basin in Brest. A corresponding numerical model was developed with a time-domain mooring modelling tool, inputting hydrodynamic data from a radiation/diffraction potential modelling program. After the calibration of several hydrodynamic parameters (added mass, damping and mean drift), the numerical model demonstrated good agreement with the experiment, providing an accurate prediction of the maximum mooring loads in irregular waves. However, results show large differences with the field test results, mainly because of the anchor position. The methods and procedures presented will allow the effective validation of numerical models to enable the development of appropriate mooring systems in wave energy applications.The authors acknowledge the support of the MERiFIC (4122) project partners (Marine Energy in Far Peripheral and Island Communities, http://www.merific.eu) and of MARINET, a European Community Research Infrastructure Action under the FP7 Capacities Specific Programme (262552) (www.fp7-marinet.eu). The authors would like to acknowledge the support of the South West Regional Development Agency for its support through the PRIMaRE institution and the support towards the FabTest through the Regional Growth Fund. The authors are grateful for the valuable support of the Ifremer team: Emmanuel Mansuy, Aurélien Tancray, Christophe Maisondieu and Peter Davies. The authors also want to thank Orcina for their technical support

Numerical model validation for mooring systems: Method and application for wave energy converters

Copyright © 2015 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Renewable Energy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Renewable Energy Vol. 75 (2015), DOI: 10.1016/j.renene.2014.10.063The design of wave energy mooring systems is challenging: overdesign incurs a significant cost penalty, underdesign may lead to a premature failure and incorrect design could reduce the power production. Consequently, compliant mooring systems are being developed for wave energy applications. This paper presents tank test results for a scale model of the buoy and mooring used at the South West Mooring Test Facility (SWMTF), an offshore facility developed to conduct long-term sea trials for wave energy device moorings. A compliant three leg catenary mooring system using Nylon ropes in the water column is investigated. Preliminary static, quasi-static, decay, regular and irregular wave tests were conducted on the 1:5 scale model, using the Ifremer basin in Brest. A corresponding numerical model was developed with a time-domain mooring modelling tool, inputting hydrodynamic data from a radiation/diffraction potential modelling program. After the calibration of several hydrodynamic parameters, the numerical model demonstrated good agreement with the experiment. However, numerical results show large differences with the field test results, mainly because of unknowns in the anchor position. The methods and procedures presented will allow the effective validation of numerical models to enable the development of appropriate mooring systems in wave energy applications.MERiFICMARINETPRIMaR

[Report of] Specialist Committee V.4: ocean, wind and wave energy utilization

The committee's mandate was :Concern for structural design of ocean energy utilization devices, such as offshore wind turbines, support structures and fixed or floating wave and tidal energy converters. Attention shall be given to the interaction between the load and the structural response and shall include due consideration of the stochastic nature of the waves, current and wind

A potential flow based underwater glider flight simulator.

International audienc

Numerical study on hydrodynamic behavior of an underwater glider.

International audienc

Experimental and numerical investigation of sloshing in anti-roll tank using effective gravity angle

International audienceAnti-roll tanks (ART) are commonly used by naval architects to deal with the lightly damped roll motion. As well as improving the roll behavior even at low or zero speed, they offer the advantage of simplicity, low cost and no extra added resistance. The investigation carried out in the present research takes part in the design and optimization of a new concept of passive anti-roll tank driven by non-linear free-surface flow phenomena and bathtub vortex (figure 1). In addition to harnessing the roll stabilizing moment from the sloshing of liquid, the kinetic energy of the vortex can be harvested using water turbines providing a new source of energy on board. The bathtub vortex (figure 2) have been studied both experimentally and numerically by Fourestier [1, 2]. Here, the focus is on the experimental and numerical modelling of the free-surface flow to properly account for the effect of sloshing in the ship global response

Round Robin Laboratory Testing of a Scaled 10 MW Floating Horizontal Axis Wind Turbine

This paper documents the round robin testing campaign carried out on a floating wind turbine as part of the EU H2020 MaRINET2 project. A 1/60th scale model of a 10 MW floating platform was tested in wave basins in four different locations around Europe. The tests carried out in each facility included decay tests, tests in regular and irregular waves with and without wind thrust, and tests to characterise the mooring system as well as the model itself. For the tests in wind, only the thrust of the turbine was considered and it was fixed to pre-selected levels. Hence, this work focuses on the hydrodynamic responses of a semi-submersible floating foundation. It was found that the global surge stiffness was comparable across facilities, except in one case where different azimuth angles were used for the mooring lines. Heave and pitch had the same stiffness coefficient and periods for all basins. Response Amplitude Operators (RAOs) were used to compare the responses in waves from all facilities. The shape of the motion RAOs were globally similar for all basins except around some particular frequencies. As the results were non-linear around the resonance and cancellation frequencies, the differences between facilities were magnified at these frequencies. Surge motions were significantly impacted by reflections leading to large differences in these RAOs between all basins