Science and Education Publishing Sustainable Energy 2 4 2014 07 02 Performance Analysis of a Water Savonius Rotor: Effect of the Internal Overlap 121 125 EN Ibrahim Mabrouki Zied Driss Laboratory of Electro-Mechanic Systems (LASEM), National School of Engineers of Sfax (ENIS), University of Sfax, B.P. 1173, Road Soukra km 3.5, 3038 Sfax, TUNISIA Mohamed Salah Abid RSE2014241 10.12691/rse-2-4-1 2014 06 18 2014 06 28 2014 07 02 The water Savonius rotor is classified as a vertical axis water rotor like the Darrieus, Gyromill or H-rotor. The advancing blade with concave side facing the water flow would experience more drag force than the returning blade, thus forcing the rotor to rotate. In this work, we are interested on the study of the of the internal overlap effect of a water Savonius rotor. The experimental results is developed using a hydraulic test bench. The test bench consists on an intake, a control gate, a penstock, a canalization, a test section, an outflow and a pump. A detailed description of the global characteristics is presented such as power, dynamic torque, power and its coefficients.