Dynamic wake modulation induced by utility-scale wind turbine operation

Abstract

Understanding wind turbine wake mixing and recovery is critical for improving the power generation and structural stability of downwind turbines in a wind farm. In the field, where incoming flow and turbine operation are constantly changing, wake recovery can be significantly influenced by dynamic wake modulation, which has not yet been explored. Here we present the first investigation of dynamic wake modulation in the near wake of a utility-scale turbine and quantify its relationship with changing conditions. This investigation is enabled using novel super-large-scale flow visualization with natural snowfall, providing unprecedented spatiotemporal resolution to resolve instantaneous changes of the wake envelope. These measurements reveal the significant influence of dynamic wake modulation on wake recovery. Further, our study uncovers the direct connection of dynamic wake modulation with operational parameters readily available to the turbine, paving the way for more precise wake prediction and control under field conditions for wind farm optimization.

Snow-powered research on utility-scale wind turbine flows

“…Here we focus on the significant implications and physical insights obtained from such deployments. For information regarding the technical details and data processing involved in these findings, please refer to our individual research papers [21,[22][23][24][25]. Using the SLPIV technique, we conducted flow measurements in the region within 0.4 upwind of the turbine at the tower plane with a field of view spanning from the ground to the elevation slightly above the hub height of the turbine.…”

“…Cross-sections of this envelope are compared to the boundary of the wake with no expansion or deflection included (referred to as the model wake hereafter), extracted from a SolidWorks model of the experimental setup. This process is described in detail in Abraham et al [22].…”

“…This additional energy flux has significant impact on the models of wake mixing and recovery at utility scale, which currently do not account for such wake modulation. For the detailed discussion regarding this work on dynamic wake modulation, please refer to Abraham et al [22].…”

Investigation of the near-wake behaviour of a utility-scale wind turbine

“…Image enhancement techniques are applied to extract these voids, and the processed images are stacked to reconstruct a quasi-three-dimensional visualization of the wake. The details of this procedure can be found in Abraham & Hong [15]. From the sample image in figure 1(f), it is clear that the bottom part of the wake is highly chaotic due to the interaction between the bottom blade tip vortices and the tower, so the wake expansion analysis focuses on the top tip where the characteristic tip vortex helix is visible.…”

“…Particularly, the work was the first to observe the occurrence of increased wake velocity indicative of wake contraction behind a field-scale turbine associated with changes in blade pitch. Subsequently, Abraham et al [14] applied SLPIV to investigate the effect of the nacelle and tower on the wake, and Abraham and Hong [15] explored the dynamic effects of turbine operation. The goal of the current paper is to combine multiple fields of view to develop a full three-dimensional understanding of novel wake behaviours observed using SLPIV.…”