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

• Published in: Renewable energy 2015-03, Vol.75, p.869-887
• Main Authors: Harnois, V., Weller, S.D., Johanning, L., Thies, P.R., Le Boulluec, M., Le Roux, D., Soulé, V., Ohana, J.
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Design engineering; Fibre rope; Fluid flow; Highly dynamic mooring system; Hydrodynamics; Mathematical models; Modelling; Mooring; Numerical model; Sciences of the Universe; Tank tests; Wave energy converter
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2014.10.063

The 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. •The numerical model of a mooring system has been calibrated.•Tank tests of a mooring typical of a wave energy device have been conducted.•Tank test results have been compared with field test results.•Use of a stiffer rope does not significantly affect the tank test results.•The radiation/diffraction potential analysis shows limitations for such tests.