Abstract
Tidal energy systems are inherently site-specific, with their potential strongly influenced by local topography and bathymetry. Field-scale simulations, supported by high-resolution digital mapping of narrow tidal channels, are crucial for capturing turbulent flow dynamics and optimizing reliable energy extraction. This study presents large-eddy simulations (LES) of a 6 km stretch of the Piscataqua River in Portsmouth Harbor, NH, to support the deployment of tidal turbine arrays under both ebb and flood conditions. The digital elevation model of the river was reconstructed using a combination of remote sensing data and field measurements. The study aims to (i) generate a high-resolution digital map of the river, (ii) evaluate the imposition of accurate turbulent inflow boundary conditions for hydrodynamic evaluation, (iii) identify potential sites based on the power density of the tidal flow predicted using LES, and (iv) assess the performance of various turbine arrays at the selected site. To represent a range of realistic tidal inflows, four inlet boundary conditions were considered: (i) a synthetic logarithmic law velocity profile applied to both tidal phases, (ii) turbulent inflow obtained from a straight-channel precursor LES, (iii) flood-tide turbulence from a 500 long river segment immediately upstream of the study area, and (iv) oceanic inflow conditions obtained from the Regional Ocean Modeling System (ROMS) model. The simulation results were used to examine local hydrodynamics and compare the performance of potential sites in the river. The findings indicate that turbulent structures and tidal asymmetry during ebb tide are the dominant factors influencing both energy output and layout optimization, with a 5 rotor diameter emerging as the most effective configuration for the site.