Within the next decade it is likely that largescale energy extraction of tidal energy at specific sites will be undertaken. Arrays of multiple devices will be installed in order to generate meaningful quantities of power to the electrical grid. Much research has now begun to focus on understanding of the effects tidal turbines have on the surrounding flow environment. This will ensure that tidal farms can be strategically positioned to achieve the maximum possible power output in any given tidal site. The objective of the analysis presented in this paper is to investigate the flow acceleration effects which occur in a tidal channel as the position of a tidal array is altered relative to the side channel boundary. Experiments involving porous actuator fences in a circulating water channel are described, and the data from these experiments is used to illustrate how the flow regime can change as a tidal array moves closer to a solid boundary. Results indicate that considerable flow acceleration can occur in certain circumstances which for full-scale arrays could affect sediment transport and marine flora and fauna. Thus arrays must be carefully located to minimise any negative impacts on the surrounding environment. This work is ongoing and aspires to shape the development of larger arrays in the medium to long term.