Cavitation observations, underwater radiated noise measurements and full-scale predictions of the Hydro-Spinna turbine

The development of marine current turbines has progressed rapidly with prototypes and full scale devices being deployed in sea. With research focusing on the hydrodynamic and design aspects of the technologies used, little is known of the impact of marine current turbine operation on marine life and environment. This paper looks at the underwater radiated noise (URN) produced from the operation of a novel tidal turbine, the Hydro-Spinna. URN measurements were taken from a 280 mm diameter model tested in Newcastle University. The model results were extrapolated to predict the full scale URN level for three turbine diameters of 5 m, 10 m and 15 m and compared to the fish reaction level acoustic level provided by the International Council for the Exploration of the Sea (ICES) as a reference. Analysis showed an increase in noise level with turbine diameters and that for all diameters, the highest noise levels were observed at Tip Speed Ratio = 1 where the thrust on the turbine is at its maximum. The noise levels predicted for the Hydro-Spinna at this off-design condition is above the ICES threshold, it was found that at optimal operating conditions the noise level would be below the threshold.