The implantation and deployment of marine current turbine arrays depend on the understanding of their interactions. Based on a priori suggestions about the layout of marine energy converter arrays, we propose to highlight interactions effects between two horizontal axis marine current turbines, in open water. experimental trials were run in IFREMER’s wave and current flume tank in Boulogne-sur-Mer (France), on marine current turbine models. Our study focuses on setups were the second turbine is axially aligned, at different distances, in the wake of the first one. Interaction effects are pointed out both in terms of performance and wake characterisation by means of a comparison with results on a single turbine. This study shows that the downstream turbine behaviour is deeply influenced by the upstream turbine wake.We also present numerical results obtained on a single turbine from our tri-dimensional numerical software, which is developed at the Laboratoire Ondes et Milieux Complexes,Le Havre (France). Those numerical results are validated by the comparison with the experiments, which allows us to foresee the modelling of several turbines and thus of turbine farms with a more complex layout.