Design and testing of a contra-rotating tidal current turbine

Clarke, J. A. and Connor, G and Grant, A. D. and Johnstone, C. M. (2007) Design and testing of a contra-rotating tidal current turbine. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 221 (A2). pp. 171-179. ISSN 0957-6509 (

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A contra-rotating marine current turbine has a number of attractive features: nearzero reactive torque on the support structure, near-zero swirl in the wake, and high relative inter-rotor rotational speeds. Modified blade element modelling theory has been used to design and predict the characteristics of such a turbine, and a model turbine and test rig have been constructed. Tests in a towing tank demonstrated the feasibility of the concept. Power coefficients were high for such a small model and in excellent agreement with predictions, confirming the accuracy of the computational modelling procedures. High-frequency blade loading data were obtained in the course of the experiments. These show the anticipated dynamic components for a contra-rotating machine. Flow visualization of the wake verified the lack of swirl behind the turbine. A larger machine is presently under construction for sea trials.