Optimization and analysis of the deflector system for a bidirectional H-type hydrokinetic twin-turbine system

Integrating deflectors enables H-type vertical axis hydrokinetic turbines (H-VAHTs) to effectively harness energy in bidirectional tidal regions. Despite advances in studies of individual turbines, a research void persists in adapting these enhancements for turbine clusters within bidirectional flows. Addressing this, this study introduces a numerical framework dedicated to refining deflector configurations, seeking to boost the performance across the twin-turbine system. The optimization results demonstrate that the turbine's average power output in the optimized twin-turbine system is 1.5 times higher than the single H-VAHT. Regarding turbine static startup, numerical results show that without deflectors, the static torque coefficients of the turbines within the twin-turbine system are nearly identical to those of single H-VAHTs. However, with the introduction of optimized deflectors, the average static torque coefficients of the two turbines increase by 46.4 % and 92.8 %, significantly improving the self-starting performance. The enhancement in performance is due to the flow collection and localized high-speed flow. Furthermore, the twin-turbine system with deflectors exhibited high power output within a range of 120° of flow direction.