The performance and hydrodynamics in unsteady flow of a horizontal axis tidal turbine.

Abstract This paper presents the effect of idealised unsteady tidal velocities on the performance of a newly-designed Horizontal-Axis Tidal Turbine (HATT) through the use of numerical simulations using Computational Fluid Dynamics (CFD). Simulations are conducted using ANSYS FLUENT implementing the Reynolds-Averaged Navier Stokes (RANS) equations to model the fluid flow problem. A steady flow case is modelling in a 2 m/s stream flow and the resulting performance curve was used as the basis of comparison for the unsteady flow simulations. A decrease in performance was seen for the unsteady flow simulation around peak TSR (TSR = 6) which has a cyclic-averaged coefficient of performance (CP) of 37.50% compared to the steady CP of 39.46%. Similar decreases in performance with unsteady flow was observed away from the peak performance TSR at TSR = 4 and TSR = 8. Furthermore, with unsteady flow that it was found that as the TSR increases, the difference between the cyclic-averaged CP and the steady flow CP drops. The effect of variations in the frequency and amplitude of the unsteady flow showed that a decrease in the cyclic-averaged CP was observed and this performance reduced with increasing frequency and increasing amplitude of unsteady incoming flows. For the cases studied here, unsteady flows are detrimental to the performance of the tidal turbine. Highlights • RANS simulations of a horizontal axis tidal turbine in steady and unsteady flow. • Comparison of the cyclic-averaged performance (unsteady) and the steady-state performance (steady) of the HATT. • The effects of amplitude and frequency variations in unsteady flow in the performance of the HATT. • Unsteady flow effects is detrimental on the performance of the turbine under study. [ABSTRACT FROM AUTHOR]

Copyright of Renewable Energy: An International Journal is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)