Three dimensional numerical simulations of a straight-bladed vertical axis tidal turbine

The generation of power from our oceans is moving to the forefront in our quest for clean and sustainable energy, and for tidal power vertical axis turbine designs are eminently suitable. Research into these turbines however has lagged behind that of other designs, and further research into their hydrodynamic flow and loading characteristics through the use of Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD) is needed to improve their efficiency and longevity. Previous CFD tidal turbine simulations have used Two-Dimensional (2D) simulation models; this work extends these simulations using Three-Dimensions (3D) to fully capture turbine flow characteristics, loading and performance parameters. These transient simulations were performed using a commercial Reynolds Averaged Navier-Stokes (RANS) solver. Theoretical momentum based models have also been developed for comparison. At low tip speed ratio (l) both CFD and momentum models predicted turbine power accurately when compared to experimental results, but as l increases CFD models without struts and momentum simulation models showed increasing simulation error due largely to strut drag effects that were not accounted for. The highest level of prediction accuracy across all l ranges was determined by the use of a 3D CFD model with struts due to the inclusion of the resultant strut drag effects.