In the energetic tracts of coastal ocean suitable for tidal turbine deployment, the fast-flowing waters carve out a range of bedforms. In the Minas Passage of the Bay of Fundy, Canada, in which there are gigawatts of harnessable energy, the bathymetry obeys an approximate power-law relationship, such that, generally, the larger the bedform the more prominent it is. These roughness elements exert a significant (form) drag on the flow, such that their characteristic length scales impact the water speeds, and hence power potential, well up into the water column.
However, in numerical models of the coastal ocean used for resource assessment and turbine array optimisation, bottom roughness is crudely parameterised, usually as a spatial constant, and is adjusted (tuned) by trial-and-error with each change in model resolution. In this paper, we implement in a model of Minas Passage a resolution-independent, spatially-varying hydrodynamic roughness parameterisation, based on length scale information obtained from very high resolution bathymetry data, and discuss the implications for power potential and turbine placement.
