Wake measurement metrics and the dependence of tidal turbine wakes on turbine operating condition

Metrics are introduced for measuring the length and width of a turbine wake. These metrics are closely examined, and their relative advantages and disadvantages are discussed. Following this, a CFD study is carried out for a model-scale tidal turbine over a wide range of tip-speed ratios, and the performance and wake of the turbine is analysed. The study indicates that wake length is relatively unaffected by the turbine operating condition beyond the near wake, but that wake widths appear to be closely related to the turbine operating condition.