In high flow velocity areas like those suitable for tidal applications, turbulence intensity is high and flow variations may have a major impact on tidal turbines behaviour. Large boils that can be observed at the sea surface are emitted from the sea floor and may interact with tidal turbines deployed in the area. The turbulent flow and its impact on tidal turbines have then to be characterized. The Reynolds number, based on the rugosity height and mean flow velocity, is rather high in this context: Re=2.5x10⁷. For that purpose, experiments are carried out in a flume tank with Re as high as achievable in Froude similitude (in the tank: Re=2.5x10⁵ and Fr=0.23) in order to study the turbine behaviour placed in the wake of seabed obstacles. The obstacle is here a canonical square wall-mounted cylinder chosen to be representative of specific in situ bathymetric variations. This obstacle produces a very extended wake embedded with large scale turbulent structures. A tri-bladed horizontal axis turbine is positioned at various positions in the cylinder wake. Using PIV and LDV measurements, the flow past the cylinder is investigated and the local and global loads on the turbine are also acquired. The turbine is considered idle or in rotation (TSR=3,4 or 5). The database created is presented in this report.