Publication: Performance optimization of a dynamically-vented savonius rotor with controllable flaps using overset meshing and taguchi methods.
Loading...
Date
2025-08
Authors
Ebrahim, Hosseini
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Recent advancements in controllable dynamic venting have enhanced the efficiency of drag-driven Savonius turbines while preserving their omnidirectional
capability, making them more viable for practical energy extraction. This study extends previous work by employing Overset meshing to improve the design and functionality of controllable flaps, allowing for more realistic hinge placement and rotation. Unlike prior approaches using the Sliding mesh technique, each flap is now hinged at the inner tip of its parent rotor blade. This new mechanism allows the flap to rotate inward and vent impinging flows more effectively during the returning sweep, thus reducing negative torques and improving aerodynamic efficiency. Verification of the flow behavior confirmed that the vented stream consistently moved inward toward the returning (concave) side, in contrast to the outward jet produced by the earlier pivoted model, thereby supporting the hypothesis and explaining the observed performance gains. Using a Taguchi-based optimization framework and Analysis of Variance (ANOVA), three flap designs and six operational parameters were systematically analyzed to maximize power output while minimizing energy consumption. The optimal configuration of a mid-half flap design, resulted in a 29% increase in the average power coefficient (CP) at the optimal tip-speed ratio (λ = 1.0), surpassing the previously reported gains of 21% and 25%. Accounting for flap actuation, approximately 12.8% of the generated rotor energy was expended on flap operation, yet the net gain in efficiency remained significant. Furthermore, the Levelized Cost of Energy (LCOE) analysis indicated that the optimized mid-half flap configuration achieved an estimated 0.73 USD/kWh, which is lower than baseline Savonius configurations and previous venting strategies, underscoring both the technical and economic feasibility of the proposed design. These findings refine the approach to dynamic venting, showing its capability to decrease negative torques and boost the Savonius rotor efficiency, especially in practical applications where omnidirectionality and low-speed performance are beneficial.