Wind Turbine Wake Interactions - The Influence of Shear on a Wind Turbine Wake

Abstract

Full wake measurements have been performed on a model wind turbine at NTNU s wind tunnel to investigate the impact of shear flow compared to uniform flow on the wake flow. Mean and turbulent velocity measurements have been performed at two downstream distances x/D = 2.77 and x/D = 5.18, while the turbine was operating at optimal tip speed ratio λ= 6. Shear flow wake shows slower recovery of velocity deficits for the lower region of the wake, while the opposite is observed for the upper section of the wake. The centre of the rotor swept area is affected by the shear flow, where low velocity fluid is transported upwards, while high velocity fluid is transported down by the wake rotation. Turbulence intensity levels are similar for the closer wake, although shows slightly decreased values downstream for the lower region of the shear wake, compared to that of the uniform flow wake. A slight horizontal movement of the tower wake was observed for the shear flow wake.