Induction study of a horizontal axis tidal turbine: Analytical models compared with experimental results

In a water channel, a scale horizontal axis tidal turbine is positioned in a low-disturbance uniform flow, and Particle Image Velocimetry (PIV) measurements are used to investigate turbulent-flow modifications in front of the turbine. The results confirm that even if the axial velocity deficit is mainly governed by the turbine rotational speed, a similar velocity profile is observed regardless of the rotational speed: the uniform flow evolves to a shear flow with a peak velocity deficit in front of the hub. The mean radial velocity component is not sensitive to the turbine rotational speed in front of the hub, whereas its amplitude increases near the tip of the blade as the Tip Speed Ratio increases. PIV database is also used to verify the validity of consolidated analytical induction models. Models based on the axial momentum theory, vortex method, and self-similar models exhibit some discrepancies with experimental measurements, especially in front of the hub. This paper proposes a turbine induction model that separately considers the influence of the hub and the rotating blades. The mean flow deficit in front of the operating turbine calculated using this new model is consistent with the experimental measurements.