Comparison of the power performance of a conventional Savonius turbine with various deflector configurations in wind and water

Savonius turbines for wind and hydrokinetic applications both operate on the same principle in terms of power generation. However, the effects of their power performance when augmented with various deflector configurations in wind and water have not been comprehensively investigated, and the comparative analysis in the literature still lacks due to the different fluid mediums. Therefore, the present study aims to evaluate and compare the power performance of a conventional Savonius turbine augmented with various deflector longitudinal positions, heights, and angles using a water channel and a wind tunnel with identical flow dynamics. The same turbine model and deflector configurations were tested at equivalent flow rates with the same Reynolds number of 1.48 × 105, corresponding to a typical flow condition in hydrokinetic applications. The turbine power performance, when operated in the wind tunnel, was found to match relatively well with the corrected results of the turbine power performance operated in the water channel, despite being tested in different fluid mediums. In addition, the trends for maximum coefficients of power for both tests are similar in terms of the variations of the deflector angles and the longitudinal positions, resulting in the same deflector parameters that contributed to the best power performance. The maximum coefficient of power, its corresponding coefficient of torque, and tip speed ratio obtained in the wind tunnel differ from the water channel results by 3.98%, 4.44%, and
1.08%, respectively. As a result, this study validates wind tunnel measurements of the power performance of Savonius turbines for hydrokinetic applications, augmented with flow deflectors. Therefore, results obtained in wind tunnel experiments can be used to evaluate the turbine power performance for hydrokinetic applications provided that the principle of flow similarity between the two mediums, wind and water, is satisfied.