Tidal turbulence in medium depth water, primarily a model study

Abstract

Tidal energy is considered to be one important future source of renewable energy. There is presently a strong development in new technology, and there is an emerging need to e.g., describe the turbulence intensity and its characteristics in a tidal stream. In this study we consider a high resolution Large Eddy Simulation (LES) in water with 80 m depth and a tidal stream with a maximum volume mean flow amplitude of 2 ms-1. the simulation is designed to describe turbulence characteristics at a developer site outside Holyhead in the Irish Sea. We find that the turbulence intensity and characteristics has clear time dependence, and that it is 100% stronger on the retarding tidal current as compared to the accelerating tidal current. We also find that it depends on the distance from the bottom. The turbulence is highly anisotropic with much longer length scales in the flow directions than perpendicular to flow direction. The simulation setup and results for mean flow quantities and turbulence measures are discussed in the presentation. Finally, results are compared with results from a ship mounted ADCP for mean flow characteristics and for turbulence quantities.