Measurements of turbulence at two tidal energy sites in Puget Sound, WA

Field turbulence data are given from two locations in Puget Sound, WA, that are being considered for tidal current turbine power production. Time series data from numerous acoustic Doppler sensors is processed to provide statistical measurements of tidal current variations in amplitude and direction. At the hub heights (i.e., the relevant depth) of the proposed turbines, the turbulence intensities (i.e., the turbulent velocity fluctuations normalized by the deterministic tidal currents) are usually 10%. The turbulence's length and temporal scales are also investigated. The turbulent kinetic energy (TKE) spectra are dominated by large-scale; anisotropic eddies, which may be due to each site's proximity to headlands. An isotropic turbulent cascade is seen at small scales and utilized to predict TKE dissipation, which is demonstrated to balance with shear generation. The importance of removing Doppler noise from turbulence statistics is addressed, as well as data quality and sample settings. The findings may be used to predict the performance and fatigue of tidal turbines.