Influence of a velocity profile & support structure on tidal stream turbine performance

With tidal turbine technology in its infancy prototype devices are likely to be positioned at locations where both the local marine environment and vessel navigation are favourable. However, as marine turbine technology develops toward economic viability there is a propensity for undesirable interactions with local shipping, higher turbulence levels and velocity shear through the water column to occur. The latter high shear could result from positioning the turbine lower in the water column, perhaps due to local shipping requirements. This paper helps to elucidate the performance of the tidal turbine and in particular the blade forces during rotation within a high shear velocity profile. A velocity profile from ADCP measurements was used as an inlet boundary for CFD analysis. The work shows that the presence of a suitably positioned stanchion downstream of the turbine will result in reduced performance characteristics over a complete rotation. However, the amplitude of the characteristics, in particular, the axial loading increases which would require careful design considerations.

► Peak power extraction occurs after TDC while rotating in a clockwise direction.
► The upstream flow field rotates due to the downstream asymmetric flow.
► A stanchion amplifies peak torque, power and thrust but lowers the mean values.
► A stanchion and upstream velocity profile influence the wake asymmetry.