Author(s): Yaling Chen, Binliang Lin, Jie Lin
Linked Author(s): Yaling Chen
Keywords: Tidal stream turbine, velocity measurements, velocity deficit, turbulence fields
Abstract: As well as estimating the extractable potential of tidal stream energy, it is also important to understand the influence of tidal stream turbine on the hydrodynamic processes. Physical experiments and numerical model simulations have both been conducted to investigate the characteristics of turbine wakes. However, detailed experimental data are still too limited to reveal the whole evolution process of the wake structure. A detailed experimental study on the effects of a horizontal axis turbine with three blades is conducted in a recirculating water flume. An Acoustic Doppler Velocimeter is employed to measure the time varying velocities across the full width of the open flume, and three-dimensional mean velocities and turbulent flow fields are subsequently obtained. Velocity deficit is clearly observed in the wake flow, while velocity change is insignificant upstream, with the velocity deficit being negligible over one rotor diameter upstream. Immediately downstream, the maximum velocity deficit occurs at the wake core due to a lower Tip Speed Ratio of the rotor. As the distance increases along the downstream, the wake strip enlarges slightly with less diffusion in the transverse direction, while the wake zone shifts towards to the water surface in the vertical direction. Furthermore, the wake turbulence is strong and anisotropic, which can impact on the behavior of turbines located downstream
Year: 2017