Effect of tip speed ratio on dynamic structural characteristics of Savonius hydrokinetic rotor

Abstract

The Savonius hydrokinetic rotor has been recognized for its large torque coefficient and non-sensitivity to incoming flow direction. However, its structural property still lacks explicit interpretation. The present study aims to elucidate the relation between flow, structural and operational characteristics of a Savonius hydrokinetic rotor. A numerical work was conducted using the method incorporating the computational fluid dynamics (CFD) technique and fluid-structure interaction (FSI) model. The results show that the rotor achieves its highest power coefficient of 0.18 at a tip speed ratio of 0.8. Instantaneous pressure distribution over rotor surface varies considerably with the rotational angle. The maximum deformation of the rotor occurs at the outer edge of the end plate, as is insensitive to the tip speed ratio. Stress concentration arises at the junction of the outer edge of the blade and end plates. As the tip speed ratio increases from 0.5 to 1.0, the peak value of the maximum deformation and stress of the rotor decrease by approximately 8 % and 18 %, respectively. Apart from locating the rotor parts subjected to high stress, this study correlates instantaneous flow field and structural performance of the Savonius hydrokinetic rotor.