Investigation of Savonius hydrokinetic turbine's 3D structural characteristics affecting cluster performance

S-VAHT clusters have become a promising approach for marine current energy utilization. However, most research has focused on cluster layout optimization, with limited attention to how 3D structural aspects like aspect ratio (AR) and twist angle (TA) affect the cluster's performance. This study fills that gap using 3-D simulations to explore the effects of AR and TA on both single turbines and clusters. Results show that the influence of AR on turbine performance is mainly related to the local flow near the end-plates, which affects the pressure distribution along the blade height. A larger AR reduces the impact of these local effects, leading to more consistent performance. In clusters, a larger AR enhances the blockage effect on the incoming flow, thereby improving overall array performance. TA has a substantial effect on the performance of both single turbines and clusters across all operating conditions, with increasing TA widening the performance gap between turbines. Furthermore, the interaction between TA and the relative azimuth angle is crucial for cluster coupling gains. Finally, the study demonstrates that TA improves the self-starting capability of turbines at specific azimuth angles. These findings provide a theoretical foundation for optimizing S-VAHT cluster design and offer innovative strategies to improve marine current energy efficiency.