الفهرس 
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Abstract
The Savonius wind turbine is known for its simplicity, outstanding cost-effectiveness and low noise, making it ideal for wind energy harvesting in urban areas. However, its success is hampered by the low coefficient of performance. Several geometrical modifications have been proposed by researchers to improve its performance. The present study aims to investigate the impact of the endplate addition and the blade shape modification in the overlap area on the coefficient of performance of the Savonius wind turbine. The unsteady Reynolds Average Navier Stokes equations and the turbulence equations corresponding to SST κ-ω were solved using the commercial CFD package ANSYS FLUENT. An endplate-integrated 3D model and an endplate-free 3D model of the same geometrical configuration of 1 m diameter and height were simulated under the condition of tip speed ratio 0.8. The extracted results were compared with the existing experimental and numerical data under the same conditions and a close agreement was reached. The endplate-filled turbine showed a significant increase in performance. The lift and drag coefficients were enhanced by 4 and 1.8 times, respectively. Flow contours of pressure, velocity and turbulence intensity were obtained at an angular rotation of 90° where there was a maximum increase in performance to explain how the endplate brings about the change. The same conventional Savonius turbine with the same geometric configuration was modified by adding two double gap flow guides at the end of the turbine blade in the overlap area. The double gap flow guides were of different lengths of 25- 100 mm and fixed at different angular positions of 45-90 degrees. Simulations were conducted in 2D and validated with 3D simulations at key points. The extracted results of the coefficient of performance and torque were compared with the available experimental data for validation iii purposes. A maximum increase of 12.24% in the coefficient of performance was observed for model 75 (degree angle) - 75 (mm length) at tip speed ratio 1. Despite the high performance for model 75-75, model 60-75 showed a higher average coefficient of performance across a wide range of tip speed ratios.