Numerical investigations on double Savonius vertical axis wind turbines with a deflector: Effects of turbine and deflector-related parameters

The present study conducts CFD simulations around double Savonius-type wind turbines with a deflector and investigates their performance variations compared to conventional (no deflector) wind turbines with respect to deflector-turbine deployment design parameters. Because the type of deflector and the method how to arrange double wind turbines with the deflector become crucial parameters that significantly impact turbine performance, this study considers subsequent four design parameters: deflector shape, deflector size, deflector-to-turbine distance, and turbine-to-turbine distance. To assess the importance of these parameters on performance, the Taguchi method is employed. Analysis of the Taguchi method results reveals that the influences of deflector shape and turbine-to-turbine distance on wind turbine performance are relatively higher than the other parameters. Performance variations in deflector-equipped double wind turbines appear to depend on the size and pattern of wakes generated behind the deflector. High-performing wind turbines are identified when the wake behind the deflector reduces the flow into the returning blade and increases the flow into the advancing blade. The best performance is achieved with 1 . 9 D -apart circular deflector-equipped double Savonius wind turbines, demonstrating a 19.65% and 8.42% higher performance than conventional single and double Savonius wind turbines, respectively.