Numerical Setup and Wake Field Study of 3d Tidal Turbines in an Array Under Realistic Flow Conditions

Abstract

This study presents a methodology for applying three-dimensional actuator disk-RANS technique in  modelling tidal energy converters within a regional-scale simulation. Of particular interest is the robustness of the applied momentum source term and its effectiveness in modelling an array of full-sized tidal turbines under realistic hydrodynamic and operational condition. The Inner Sound region, which is the site of commercial-scale deployment projects of the Pentland Firth in Scotland, is chosen as the study area. While actuator disk approach had been used in past studies to parameterise the far wake region of horizontal-axis tidal turbines, details of its three-dimensional implementation have not been thoroughly discussed. Criteria adopted in deciding the array location are presented in this study, along with the actuator discs’ detailed setup and constraints. The models are subjected to operational characteristic that is similar to commercial devices in service to examine the accuracy of the imposed source term under complex flow condition. The results demonstrate that the thickness of the disk imposed in the source term has a pronounced influence on the model outputs. In addition to accurately modelling flow propagation and wake interactions, the models are also able to replicate the observed asymmetrical tidal currents in the region. As there is currently limited published material on the detailed application of the actuator disk approach in ocean- scale models, it is hoped that this study will fill the research gap and provide evidence, guidance, and examples of best practices for future studies.

Keywords: Pentland Firth, flow interactions, actuator disk, hydrodynamic characteristic, Telemac3D