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

Research output: Contribution to journalArticlepeer-review

Abstract

Introducing a duct along the perimeter of a tidal turbine has been acknowledged to sustain rotor performance. The causation behind the outcome of 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 m.s-1 to 7 m.s-1 22 , and a bearing angular range of 0o to 45o 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 23.2o 25 , 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
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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