CFD performance enhancement of a low cut-in speed current Vertical Tidal Turbine through the nested hybridization of Savonius and Darrieus

OpenFoam code was used to evaluate the hydrodynamic performance of the nested hybrid turbines, and to investigate their torque and power coefficients. This code is based on an Unsteady Reynolds Averaged Navier Stocks (URANS) approach coupled with k-ω Shear Stress Transport (SST) turbulence model. URANS models were validated against the literature results by performing 2D simulations on Savonius and Darrieus wind turbines. Therefore, the turbine's behavior was studied and the overall performance efficiency of the nested hybrid design was enhanced over a defined Tip Speed Ratio (TSR) range. The main founding of this study was that the hybrid asynchronous coupling of Savonius and Darrieus (Identical rotational direction for the two rotors) is providing the effective performances compared to the other hybrid studied configurations.