To address the problem of the imminent energy crisis, pollution from fossil fuels, and global warming, it is necessary to incorporate renewable technologies. In that context, the drag-based Savonius wind turbine has tremendous potential to extract wind energy and can be operated as a standalone system at remote areas where the conventional electricity cannot be provided. The present study primarily focuses on the performance evaluation of a conventional semicircular-bladed Savonius rotor with capped vents (CVs) or nozzle chamfered vents. The rotor blades having vent ratios of 7%, 14%, and 21% are tested in a wind tunnel, and subsequently, their performances are compared with a rotor without CVs under identical test conditions. Computational fluid dynamics (CFD) simulations have also been carried out to compliment the surprising experimental results and also to analyze the flow physics around the rotor blades. From the understanding of torque distribution, it has been noticed that the performance of the rotor with CV deteriorates compared with the conventional semicircular-bladed rotor. The vents are found to decrease the positive torque and increase the negative torque by disturbing the pressure distribution of the conventional semicircular-bladed Savonius rotor.

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