Geometrical parameter’s effects on the hydrodynamic characteristics of the horizontal axis open-center ducted tidal turbine

Tidal current energy is a predictable and sustainable renewable resource, and ducted turbine concepts, particularly open-center ducted tidal turbines have demonstrated potential for enhanced hydrodynamic efficiency compared to conventional configurations. Despite their industrial deployment, the influence of key geometrical parameters of the open-center configuration on turbine performance and flow behavior is not yet fully understood. This study investigates how variations in chord length, pitch angle, thickness, blade number, and open-center radius influence the hydrodynamic behavior of open-center ducted tidal turbines. The numerical model was validated against experimental data for a conventional three-bladed marine turbine and numerical results for an open-center geometry using three-dimensional computational fluid dynamics simulations. Simulations were conducted under a uniform inflow velocity of 1 m/s and tip speed ratios ranging from 1.0 to 2.5. The effects of individual and combined geometrical modifications were assessed relative to a numerically validated baseline model. The results indicated that reducing the open-center radius increased the power coefficient by an average of 6 %. Furthermore, a maximum 6 % increase in the power coefficient was achieved at low tip speed ratios using a reduced chord length combined with a greater number of blades. The highest improvement of 9.98 % in power coefficient was observed at higher tip speed ratios when pitch angle modification was combined with changes to the chord and blade number. Pressure distribution and flow field analysis are also presented, demonstrating that geometrical tuning can significantly enhance turbine performance across varying operating conditions.