CFD modelling of vertical-axis wind turbines using transient dynamic mesh towards lateral vortices capturing and Strouhal number

Abstract

This study investigated the aerodynamic performance of vertical-axis wind turbines (VAWTs) with a focus on optimising their design to enhance energy capture through lateral vortex dynamics, an aspect crucial for improving efficiency but often overlooked. Advanced Computational Fluid Dynamics (CFD) simulations were performed using a transient dynamic mesh approach to analyse the aerodynamic behaviour of three distinct VAWT prototypes under varying wind conditions. The results demonstrated that kinetic energy and torque were significantly enhanced with increasing inlet velocity. A maximum torque of 5.5 Nm was achieved by the two-blade Savonius turbine across wind speeds from 5 to 14 m/s, outperforming the helical Savonius turbine, which reached a peak torque of 2.5 Nm at 14 m/s. The two-blade turbine also attained a peak velocity of 19.1 m/s at 11 m/s, exceeding the helical turbine’s 13.3 m/s. This performance comparison clearly highlights the potential of the two-blade Savonius turbine in enhancing wind energy efficiency. Additionally, the incorporation of end plates in the helical turbine resulted in a 24.1% increase in maximum torque, demonstrating improved airflow regulation and turbine efficiency. Vortex shedding analysis revealed that Strouhal numbers ($\mathrm{St}$) ranged from 0.05 to 0.130 for the two-blade turbine and from 0.040 to 0.070 for the helical turbine, with further reductions to 0.028 to 0.052 when end plates were added. These findings highlighted the critical role of lateral vortices in optimising turbine performance and demonstrated the potential of this approach for validating large-scale wind cluster simulations. Ultimately, new insights into VAWT aerodynamics were provided, paving the way for improved turbine design and enhanced wind farm efficiency.