Experimental investigation of the wake of a horizontal axis tidal current turbine by LDV

A scaled-model of an HATCT (Horizontal Axis Tidal Current Turbine) was tested in the CNRINSEAN Circulating Water Channel. Two different analyses were performed during the experiments: preliminary investigation of the performances of the turbine in different working conditions and LDV (Laser Doppler Velocimetry) measurements in the near wake. Velocity measurements are performed in phase locking to the rotor, in order to resolve the blade wake structure at different working regimes. Indeed, the knowledge of all three velocity components (tangential, axial, radial) allows to evaluate through energy balance concerns, the transfer of inflow kinetic energy into mechanical work of the rotor and into different energy contributions in the wake. The LDV analysis of the near wake also contributes to understand some of the most important fluid dynamics aspects related to the design of the rotor and to the different working conditions, and can be used as a preliminary study for understanding the wake evolution and the interaction between two or more turbines in a farm.