A three-dimensional regional scale model for tidal stream turbine implementation and impact assessment

This research aims to implement a threedimensional regional scale numerical model within a region of the Irish Sea (between 52.808˚N and 53.842˚N) that is suitable for turbine array implementation and impact assessment. This research is based on a three-dimensional wave-current-sediment fully coupled oceanographic model (FVCOM), and modifications made by the authors to the current, turbulence and surface wave modules to simulate the potential impact of tidal turbines. The baseline model, i.e. without turbine implementation, is validated extensively against water level measurements at two tide gauges, tidal current data collected at four locations, and wave climate collected by a WaveNet bouy. In the case study, 18 turbines of 15-20 m diameter are modeled individually in the waterway between Anglesey and the Skerries. Results reveal the potential effects of the turbine farm on flow field, turbulence kinetic energy (TKE), bed shear stress and surface waves. Defining the wake edge as flow recovery to 95% of the baseline case, there are slight wake effects for a distance of around 14 times the array width downstream of the device farm. As a result of the high spatial resolution used, local effects of the turbine farm are revealed by the model, such as flow acceleration on both sides of the turbine farm, flow acceleration near the bed in the vicinity of the turbine farm which leads to enhanced bed shear stress, and locally increased TKE