ABSTRACT
Alderney Race is a site with high tidal-stream energy potential. Current velocity measurements by two bottom-mounted ADCP are used to assess the variability of velocity and turbulence in the water column. Turbulence metrics such as the dissipation rate (ε) of turbulence kinetic energy and the integral lengthscale (L) were estimated through the spectral approach and compared to the turbulence intensity (I). The mooring locations match areas with very different turbulence regime. At the northern ADCP site, characterized by higher current speed, all turbulence parameters were found larger. This enhancement is assumed to result from the current interaction with irregularities of the bathymetry and the friction effect. At the southern site, over a relatively smooth bathymetry, the temporal variability of turbulence was found depended on the velocity shear. These results highlight large spatial variability in turbulence characteristics occurring at rather short distance (4 km) within the prospective site.
