A numerical swallowing-capacity analysis of a vacant, cylindrical, bi-directional tidal turbine duct in aligned & yawed flow conditions

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Borg, Mitchell G. and Xiao, Qing and Allsop, Steven and Incecik, Atilla and Peyrard, Christophe (2021) A numerical swallowing-capacity analysis of a vacant, cylindrical, bi-directional tidal turbine duct in aligned & yawed flow conditions. Journal of Marine Science and Engineering, 9 (2). 182. ISSN 2077-1312 (https://doi.org/10.3390/jmse9020182)

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Abstract

Introducing a duct along the perimeter of a rotor has been acknowledged to augment turbine performance. The outcome causation due to a bi-directional, cylindrical shroud, however, is uncertain. This study analyses the hydrodynamic swallowing capacity of a true-scale, vacant duct for tidal turbine applications in aligned and yawed inlet flow conditions by utilising three-dimensional unsteady computational fluid dynamics. The performance is investigated within free-stream magnitudes of 1 to 7 m.s −1, and a bearing angular range of 0° to 45° with the duct axis. In proportion to the free-stream magnitude, the normalised axial velocity through the duct increases as a result of a diminishment in pressure drag. Within yawed flow, the maximum capacity falls at a bearing of 23.2°, resulting in a performance increase of 4.13% above that at aligned flow conditions. The analysis concludes that the augmentation at yawed flow occurs due to the duct cross-sectional profile lift variation with angle-of-attack. Towards nominal yaw angle, the internal static pressure reduces, permitting a higher mass-flow rate. Beyond the nominal angle-of-attack, flow separation occurs within the duct, increasing pressure drag, thereby reducing the swallowing capacity.

ORCID iDs

Borg, Mitchell G., Xiao, Qing ORCID logoORCID: https://orcid.org/0000-0001-8512-5299, Allsop, Steven, Incecik, Atilla and Peyrard, Christophe;
CORE (COnnecting REpositories)