The shape of turbulence generated at highly energetic tidal sites*

Turbulence models that assume isotropic turbulence fail to accurately capture the anisotropic characteristics of highly energy tidal sites. Unanticipated anisotropies in the flow could introduce high force fluctuations on tidal energy devices leading to blade/component fatigue and a reduction of the device lifespan. Energy estimates could also be adversely affected. The current study analyzes the anisotropic behavior of turbulence from various tidal energy sites worldwide. Anisotropy for each site is evaluated using a Lumley triangle, a visualization tool that was developed to describe the shape of turbulent eddies (structures) in a flow. The effect of mean flow velocity and turbulence intensity on the shape of the turbulence and the degree of anisotropy at each site will be discussed. Preliminary results suggest the full range of turbulence shape is site-specific, though all sites analyzed demonstrate the majority of data exhibits axisymmetric, oblate spheroid-shaped turbulence. The implications of such turbulence shape and the instances of deviation will be presented.