Turbulent flow mapping in a high-flow tidal channel using mobile acoustic Doppler current profilers

In this investigation, instrumented mobile platforms are used to spatially map the turbulent flows in Grand Passage, one of the Bay of Fundy's more energetic tidal channels in Nova Scotia, Canada. The aim is to characterize the flow around the PLAT-I floating tidal energy platform developed by Sustainable Marine Energy Canada (SMEC). GPS-tracked surface drifters equipped with fast-sampling acoustic Doppler current profilers (ADCPs) provide turbulence-resolving vertical profiles of velocity and turbulent kinetic energy dissipation rate along drifter trajectories, while vessel-mounted ADCP transects complement the mean flow velocity measurements. These data are used to construct tridimensional quasisynoptic maps of mean velocities and turbulence parameters for several stages of the tide around PLATI's location including peak ebb and flood currents. The data set includes measurements under natural flow conditions, and while the turbines installed on PLAT-I were both not operational and operational. The measurement techniques and resulting maps successfully capture the spatial and temporal structure of the flow for unsteady conditions for various tidal conditions. The combined wake of the four 6.3 m operational PLAT-I turbines was measured for a single tidal stage. Closer to the turbines, the vertical extent of the wake is about 6 m (approximately one turbine diameter), increasing with distance downstream, while the maximum observed velocity deficit is 26% relative to not operating conditions, decreasing with distance downstream.

Automated summary

In this study, instrumented mobile platforms were used to map the turbulent flows in Grand Passage, one of the Bay of Fundy's energetic tidal channels in Nova Scotia, Canada. The aim was to characterize the flow around the PLAT-I floating tidal energy platform developed by SMEC. The data collected through GPS-tracked surface drifters equipped with ADCPs and vessel-mounted ADCP transects successfully captured the spatial and temporal structure of the flow under different tidal conditions.