High Reynolds number tidal race environments, attractive for development of in-stream tidal energy generation, are known to contain Coherent Structures. Coherent structures are turbulent boundary layer structures that translate vertically through the water column and are expressed on the surface as boils. Their local vorticity over small distances and large velocity shear contribute to high mechanical failure rates of tidal energy turbines. These coherent structures are also known to transport sediments, pollution, and phytoplankton blooms. Metrics for measuring these phenomena are not well defined. Many studies of marine potential energy sites have used the standard International Electrotechnical Commission (IEC) metric for quantifying turbulence at wind sites; the turbulence intensity. However, discrepancies in turbulence intensity and power densities in marine environments suggest that this metric does not capture coherent structure information as such, new metrics appropriate
to water turbine design and prediction of fatigue loads are needed. The aim of this thesis is to develop and test new methodologies, using measurements from an off-the-shelf ADCP correlated with visual quantification of surface boils, to provide a more appropriate and comprehensive characterisation of turbulence at the scales, structure/coherency and stress which are most likely to compromise the structural integrity of the tidal energy infrastructure and its operational performance.