A CFD study on the performance of a tidal turbine under various flow and blockage conditions

CFD simulations utilising the actuator disk model have been performed to study the effect of various parameters on the thrust produced by a tidal turbine. Instead of increasing the performance coefficients of the turbine, a turbine placed in blocked conditions is shown to experience a velocity higher than the inflow velocity using a new approach to interpret results from CFD simulations. Turbines were found to produce less thrust when boundary layers were present than when boundary layers were absent in the simulation. Also, the presence of the boundary layer results in an optimal aspect ratio where the performance of a single turbine is maximised. Besides turbulence intensity, the flow velocity is also found to affect the predicted thrust of the turbine. Thrust increases with increasing blockage ratio when channel depth is held constant, and also increases with channel depth while blockage ratio is held constant. The rate of decay of turbulence intensity in the channel is also observed to be dependent on the channel depth, which may have affected results. Thus, the effects of blockage on turbine performance should be studied by varying the channel width without changing the channel depth.