Volumetric velocimetry of the near wake of a model wind turbine*

For the purpose of commercial power production, wind turbines are often clustered together in wind farms. In such situations, some of the turbines will frequently operate in the wakes generated by the upstream turbines. As wake operation changes the inflow conditions of downstream turbines, characterisation of the wind turbine wake is important. Wind turbine wakes are inherently three-dimensional flows. Therefore, employing three-dimensional measurement techniques to capture the full wake structure would be insightful. This work presents volumetric velocity measurements of the near wake of a freely rotating, two-bladed model wind turbine at a Reynolds number of 18000. The measurements were obtained using the state-of-the-art velocimetry technique Shake-the-Box in a free surface recirculating water channel. The volume of interest measured 13.5 cm by 13.5 cm by 10 cm and was illuminated by high-power pulsed LEDs. The goal of the study is to characterise the three-dimensional flow features and flow structures generated by the rotor. We also investigate how these structures interact with the wind turbine tower.