1. Introduction Fast tidal currents of interest for power generation often occur close to islands or headlands, where flow separation can occur and cause large areas of recirculation, extending over many kilometres. This is the case for a number of sites identified as having high potential for development, notably the Pentland Firth to the south of the island of Stroma [1–3]; at Portland [4] (a headland on the south coast of the UK) and Alderney [5] (an island in the Normandy-Brittany Gulf).
