Effects of the distance ratio of circular flow disturbance on vertical-axis turbine performance: An experimental and numerical study

A Darrieus turbine, one type of Vertical-Axis Turbines (VATs), has relatively poor performance compared to Horizontal-Axis Turbines (HATs) and has limited self-starting capability in low current velocities. The presence of a circular flow disturbance in front of the turbine can significantly affect its performance. This study aims to identify the most effective configurations for flow disturbances by varying horizontal distances and diameter ratios. The experimental study was conducted at the ITS towing tank facility to assess the performance of VAT, especially in low current velocity environments. Additionally, a numerical study using Computational Fluid Dynamics (CFD) software was employed to examine the impact of flow disturbances and analyze the fluid flow pattern behind them. Cylindrical flow disturbances were introduced at different horizontal distances from the turbine, with variations at x/D 0.0, 0.5, 1.0, and 1.5. The ratio of the flow disturbance to the turbine diameter (ds/D) was also varied at 0.3 and 0.5 for comparison. The results indicated that a flow disturbance placed at x/D 0.0 distance from the turbine and a diameter ratio (ds/D) of 0.5 yielded the most favorable configuration, resulting in an average power coefficient (Cp) increase of 28.4% compared to the turbine without a flow disturbance.