Abstract
Uncertainty in tidal turbine loading contributes significantly to conservatism in turbine design. This uncertainty originates not only from a lack of knowledge of the flow field at a particular site, but also from lack of understanding of the fundamental physics which govern the loading and performance of tidal turbines in unsteady and turbulent flow regimes. In order to reduce this conservatism and the costs associated, the mathematical and engineering models used in turbine design must be improved. To facilitate the development of these models requires scale experimental data for validation. However, few well-documented experimental data sets are available for tidal turbines, especially at scales large enough to achieve Reynolds number independence and comparability to full scale devices. This paper reports on the initial phases of a tidal turbine benchmarking project that will conduct a large laboratory scale experimental campaign on a highly instrumented 1.6m diameter tidal rotor. The turbine will be tested in well defined flow conditions, including unsteadiness created by free surface waves, as well as freestream turbulence, with instrumentation to determine edgewise and flapwise loading distributions along the blades as they rotate through the unsteady flows. As towing tanks by their nature have low levels of freestream turbulence, a carriage-mounted turbulence grid will be utilised to generate sufficient freestream turbulence in a well-defined manner. In this paper the turbine geometry and test conditions are specified, as well as providing details of the rotor’s hydrodynamic design process. Additionally, the results of a flow characterisation of the carriage-mounted turbulence grid via Acoustic Doppler Velocimetry are presented. The turbulence grid produced a mean turbulence intensity of 3.5% across the region in which the turbine will be tested, and a very uniform flow profile of 0.913 times the upstream velocity