Abstract
A simple conceptual model of an array of tidal stream generators is a series of porous fences subject to flow in one direction, neglecting lateral velocity variations, but allowing for vertical velocity shear. In the far-wake of a fence deep inside the array, the flow might be expected to have reached an equilibrium, where the longitudinal pressure gradient is balanced by the drag of the fences and the friction on the sea-bed. This paper compares two approaches to estimating the downstream decrease in velocity in multiple-row tidal fences; firstly a simpli- fied model using ideas from boundary layer theory pre- viously applied to wind turbine arrays; second, a CFD simulation of the flow field around a ten-row array us- ing a general purpose off-the-shelf RANS Finite Volume solver. The CFD simulations have been themselves com- pared with measurements gained in a laboratory flume.