Initial Flow Characterisation Utilising Turbine and Seabed Installed Acoustic Sensor Arrays

Duncan Sutherland, Brian Sellar, Samuel Harding, Ian Bryden

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Flow velocity measurements from acoustic sensors mounted both on mid-channel depth tidal turbines and on the seabed are presented for the Fall of Warness in Orkney. The tides are analysed in one hour phases in order to investigate the evolution of metrics over the semi-diurnal cycle. The site is characterised by mean velocity magnitudes and their variation with depth, velocity direction and corresponding variation with depth (twist of the depth profile) and the turbulence intensity and its variation with depth. Analysis shows the maximum velocities of the tides at the site to be within 4◦ of bi-directionality at a reference ‘point’ 13 m above the turbine with the ebb tide exhibiting greater velocity magnitude as expected from previous site surveys. Variation between the tides is also evident in the twist of the depth profiles which is more pronounced in the slower flood tide, up to a maximum of 7◦ between the turbine and the surface. In general, both twist of the depth profile and directional variation is greatest at the lowest flow speeds. Mean turbulence intensity is shown to increase near the surface despite no significant drop in the mean velocity, particularly for the ebb tide, indicating wave orbital motion may play a role in near surface fluctuations. Finally a comparison of newly available data from a seabed-deployed ADCP with a Turbine mounted sensor shows a similar velocity depth profile curve but with a mean velocity deficit that is inconsistent over the diurnal cycle. The spatial variation of velocity (and consequent loading) over the rotor
Original languageEnglish
Title of host publicationProceedings of the European Wave and Tidal Energy Conference
Publication statusPublished - 2 Sep 2013

Keywords

  • Acoustic Doppler Instruments
  • Site Characterisation
  • Tidal Energy
  • ReDAPT

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