Abstract
Horizontal-axis tidal turbines (HATTs) play a crucial role in harnessing substantial amounts of green renewable energy from marine tides. To enhance power generation efficiency and reduce maintenance costs for individual turbines, a counter-rotating HATT with a centrosymmetric hydrofoil, hereinafter referred to as BCrTT (bidirectional counter-rotating HATT), was designed in this study. To comprehensively evaluate the performance and near-wake characteristics of the BCrTT, a validated three-dimensional (3D) numerical model incorporating the k-ω SST turbulence model and sliding mesh method was employed. The results demonstrate that the BCrTT achieves a peak power coefficient of 47.6 %, which exceeds that of the bidirectional HATT (BHATT) with a single rotor by approximately 7.9 %. Moreover, the presence of circumferential flow generated by the front rotor has a significant impact on the performance of the rear rotor. Finally, the time-averaged performance of the BCrTT remains robust, demonstrating resilience to a 10° misalignment. However, it is observed that the transient performance of the rear rotor is notably affected by misalignment, as the wake of the front rotor is unable to fully cover the rear rotor in misalignment cases.