Contribution to the CCP-WSI Blind Test Series 3: Analysis of scaling effects of moored point-absorber wave energy converters in a CFD-based numerical wave tank

Abstract

Computational fluid dynamics (CFD) based numerical wave tanks (NWTs) can provide valuable insight into the hydrodynamic performance of wave energy converters (WECs). Being able to capture hydrodynamic non-linearities, CFD-based NWTs (CNWTs) allow the analysis of WECs over a wide range of test conditions, such as sea states, power take-off control settings and model scale. The capabilities of a CNWT are exploited in this paper, which aims to analyse of the scaling effects of two moored point-absorber type WECs, exposed to focussed waves. To this end, three different scales are considered: 1:1, 1:10 and 1:10PWT. The latter, 1:10PWT scale, refers to the typical scale used in physical wave tanks (PWTs), complying with Froude scaling, but violating Reynolds scaling. In the 1:10 scale model, fluid viscosity is scaled, in line with the geometric properties, thereby achieving both Froude and Reynolds similitude. From the results, average differences between the three considered scales of around 5% have been observed, and the overall greatest sensitivity to scale effects can be found in the surge and pitch degree of freedom