Experimental investigations on Darrieus straight blade turbine for tidal current application and parametric optimization for hydro farm arrangement

The energy flow rate per unit flow area of water flow is quite high compared to air flow. This is because of high density of water compared to that of air. Hence, hydrokinetic turbine has the potential to extract more power compared to wind turbine for the same size of a turbine. The Darrieus turbine is one of the best options which can be used as a hydrokinetic turbine due to its high coefficient of power. In present work, the experimental investigations are carried out to study the hydrodynamic performance of three bladed Darrieus turbine with NACA0015, NACA0018 and NACA4415 blades for different solidities. Maxwell's velocity correction method is used to account for blockage effect. NACA0015 and NACA0018 provide highest coefficient of power of 0.15 at a solidity of around 0.382. Experiments are extended to evaluate performance for four bladed rotors with symmetric-NACA0018 and cambered-NACA4415 hydrofoils. Both the hydrofoils provide a coefficient of power of around 0.13 but at different solidities. The effect of spanwise and streamwise distance on performance of a Darrieus turbine is investigated for its use as hydrofarm. A minimum distance of 7D along the streamwise direction and 3D along the spanwise direction are essential in a hydrofarm using Darrieus turbines.