A Survey of Turbulence Characteristics at Six Tidal Energy Sites*

The design and operation of hydrokinetic turbines that convert kinetic energy from tidal currents to electricity must account for the turbulence effects over a wide range of scales. Herein, we review and compare turbulence measurements collected with high-resolution acoustic Doppler velocimeters at half-a-dozen tidal energy sites worldwide to survey the range of turbulence characteristics observed. A consistent data collection, analysis, and reporting procedure are applied to allow an apple-to-apple comparison of turbulence metrics. This procedure could serve as an industry standard to guide the characterization of turbulence at tidal sites, focusing on turbulence intensity, turbulent kinetic energy, integral length scales, and velocity spectra and their distribution in the water profile and their temporal variation within the tidal cycle. Comparisons are made between the vertical distribution of normal Reynolds stresses from ADV measurements and those predicted using empirical models developed for developed turbulent boundary layers in open-channel flumes.