Modelling extreme wave conditions for survivability tests of wave energy converters: CFD versus model tests

Abstract

<p>This study investigates the experimental and numerical generation of realistic extreme waves in the Model Test Basin (MTB) at the Australian Maritime College, University of Tasmania, in order to test the survivability of offshore structures such as wave energy converters. The sea state and maximum wave height considered were collected during Tropical Cyclone Oma as it tracked down the Queensland Coast of Australia in February 2019. Upon successful generation of a repeatable experimental sample, the NewWave theory was used to regenerate the MTB surface elevation in a STAR-CCM+ computational fluid dynamics (CFD) numerical wave tank. The experimental surface elevation data was analysed with a fast Fourier transform to obtain the wave component amplitudes (a<sub>n</sub>) and phase angles (ε<sub>n</sub>).  These parameters were then used to generate a polychromatic wave in CFD. The 2D CFD simulations were extended to a 3D simulation that included an oscillating water column wave energy converter as per the experimental conditions. Results indicate that experimental focused wave groups can be replicated in CFD software with a similarity of 0.9407 for 2D simulations.  However, by applying an amplification factor to the crest amplitude of the focussed waves, one may further obtain improved accuracy in both 2D and 3D simulations. Further mesh resolution studies surrounding the oscillating water column may improve the accuracy of 3D fluid structure interaction simulations when investigating survivability.</p>