WAVE-CURRENT-TURBULENCE INTERACTIONS IN A HIGH-FLOW TIDAL CHANNEL

Abstract

Grand Passage has been identified for in-stream tidal turbine development as a predictable, high power density, renewable energy source, and is the site for this work. A shore-connected bottom mounted Acoustic Doppler Current Profiler (ADCP) sampling at 2 Hz for 10 days in January/February 2015 spanning a storm with 80 km/h northerly winds recorded tidal current maximum speeds of approximately 2 m/s. Wave height and wave number are estimated from the velocity variance vertical structure in the gravity wave band. Independent estimates of the wavenumber are obtained from the measured phase speed, and compared to the predictions of linear wave theory, including the effects of vertical shear. The analysis also yields an estimate of the turbulence dissipation rate. Maximum wave heights were approximately 2 m, when current and waves oppose. During low wave conditions, the mid-depth turbulent dissipation rate was O(10−4) W/kg, and increased with larger waves.