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Wake characteristics of Horizontal Axis Tidal Stream Turbines in uniform and non-uniform steady flows

Date: November 05, 2013 at 15:40 GMT

This paper reports the results of a detailed experimental study to characterise the near-wake of a model Horizontal Axis Tidal Stream Turbine (diameter = 0.5m). The turbine can be assembled with different numbers of blades, so that two, three, four and six blade configurations have been investigated; the blade pitch angle has been varied accordingly to achieve optimum conditions,i.e. maximum power. Both the power coefficient and thrust coefficient are measured concomitantly. The turbine has been tested in the University of Liverpool high-speed water channel with an average inlet velocity set at 1m/s such that Reynolds numbers effects are negligible and the model results are characteristic of the full scale. In addition to uniform upstream flow conditions, a non-uniform “flow profiler” has been developed to produce a power-law velocity profile.
Three-dimensional measurements of the mean velocities and turbulence statistics have been obtained using an Acoustic Doppler Velocimeter (ADV). These measurements are taken up to seven turbine diameters downstream the turbine for a series of spanwise profiles at various depths to fully map the near-wake flow field. 

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