NUMERICAL MODELLING OF RESPONSES OF OFFSHORE WAVE ENERGY CONVERTERS IN EXTREME WAVES

Abstract

Wave Energy is a promising sector for sustainable low-carbon energy production. Despite the effort put in the last decade, concerning problems remained unsolved. Numerical modelling can play a key role in the assessment of extreme responses necessary to the understanding of Wave Energy Converter (WEC) capacity to survive extreme conditions. However, high-fidelity codes are too time-consuming for industries, while codes of lower fidelity are based on major physical assumptions inducing concerning uncertainties.

Therefore, the present study - sponsored jointly by DNV GL and the University of Plymouth - develops an hybrid model coupling the low-fidelity model WaveDyn, with a Computational Fluid Dynamic (CFD) Numerical Wave Tank validated against physical experiment of a single moored WEC under extreme events. A time-splitting technique allows to change between code as a function the confidence on the solution. The wave steepness is used to identify the limit in confidence for WaveDyn on survivability assessment. Additional developments allow to ensure a satisfactory start of the (CFD) simulation from an advance time where the wave-field is developed and the device is in motion. The coupled model overcomes identified inaccuracies in the WaveDyn code due to the inviscid assumption and the high computational cost of the OpenFOAM code.