A scaled horizontal axis tidal stream turbine with bottom-supported pile foundation was manufactured to experimentally investigate the near-wake in the recirculating water channel. Different inlet velocities and mounting heights conditions were measured at diverse points across the width and the height of the channel by an ADV which can provide detailed three-dimensional mean and turbulent flow field information. The results reveal that the three peaks of the turbulent kinetic energy behind the turbine shall change the flow field grievously. Finally, a more complicated region downstream under the centre-line of blades is found because of the still pile foundation.
In recent decades, the global increasing demand for energy has led to considerable interest in renewable energy sources and many efforts have been made in developing the alternative renewable energies. Tidal stream energy, one of the most interesting renewable and clean energy resources for electricity generation, gains more and more attention due to its reliable and predictable nature. In order to make the best of this energy, the installation of multiple devices within tidal stream turbine arrays which are both spatially efficient and sustainable is devised. Consequently, understanding the flow field downstream of a single turbine becomes the first job towards the arrangement of tidal stream turbine arrays.
There are three common ways to investigate the hydrodynamic performance and surrounding flow motion of tidal stream turbine, including numerical simulation, laboratory measurement and field observation. Numerical simulation has lower cost and is time-saving, but date of simulation may be inaccurate and require a proven library program. Laboratory measurement becomes popular due to its significantly low cost and convenience to undertake, although laboratory model may not truly simulate the real complex offshore conditions. Software capable of 3D flow modelling, taking into account the non-stationary evolution of the wake emitted by a tri-bladed horizontal axis turbine, is developed in order to assess the effects of disturbances generated on its immediate environment. Currently, we are able to simulate the behaviour of a turbine and to determine the performance of the emitted wake (Pinon and Mycek et al., 2008; Mccombes and Johnstone et al., 2009). The dynamics of farms consisting of multiple devices placed in arrays will also be analyzed. These numerical tools will be used prior to the installation of tidal stream turbine arrays, which are aiming for quantifying the interactions with turbines.
