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

Mitchell G. Borg, Qing Xiao, Steven Allsop, Atilla Incecik, Christophe Peyrard

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1 Citation (Scopus)
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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.

Original languageEnglish
Article number182
Number of pages22
JournalJournal of Marine Science and Engineering
Volume9
Issue number2
DOIs
Publication statusPublished - 10 Feb 2021

Keywords

  • swallowing capacity
  • duct flow
  • ducted turbines

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