Investigation of near wake modulation induced by utility-scale turbine operation

Super-large-scale flow visualization using natural snowfall has been implemented on a 2.5 MW horizontal-axis wind turbine (EOLOS turbine) to extract qualitative and quantitative information about the utility-scale turbine wake at unprecedented resolution, revealing the influence of incoming flow and turbine operation on near-wake behavior. However, past visualization studies were only conducted on streamwise-wallnormal planes, limiting analysis of spanwise wake behavior. In this study, we present a 3-hour video dataset that captures the full cross section of the EOLOS turbine wake at 0.2 rotor diameters downstream of the turbine, with the light sheet oriented parallel to the rotor plane. Based on Taylor’s frozen hypothesis, these plan-view images are stacked over time to visualize the temporal variation of coherent flow structures in the near wake. Specifically, the wake envelope marked by the positions of helical tip vortex structures allows us to quantify the deflection as well as the expansion/contraction of the wake. These wake behaviors are then correlated with turbine operational parameters such as yaw error, blade pitch, etc. to provide insight into the wake modulation associated with flow-turbine interaction.