In wind energy technology, predicting the evolution of wind turbine wakes under different atmospheric conditions is important for optimizing power production from a wind farm and mitigating damaging loads on the turbines due to detrimental wake interactions. This project aims to investigate the origin, evolution and regeneration of what are called very-large-scale motions (VLSMs) that evolve in the layer of air near the blade surface, termed the atmospheric boundary layer (ABL), and their interactions with utility-scale wind turbines. As the scale of wind farms continues to grow and as wind turbines increase in size, VLSMs are expected to profoundly influence wind power production and the downstream evolution of wind turbine wakes. However, the origin and dynamics of VLSMs are not well understood in some cases, and therefore their effects and interactions with utility-scale wind turbines are difficult to predict. This project advances numerical simulations and proof-of-concept laboratory experiments on this topic. Additionally, undergraduate students are being trained to measure wind velocities at the University of Texas Dallas mobile LIDAR (Light Imaging, Detection, And Ranging) station, which is a unique facility for education and outreach activities. This training impact students from a wide range of backgrounds and makes them aware of important topics, such as meteorology, extreme weather phenomena, anthropogenic effects on the environment and renewable energy.
The goals of this research project are to: 1) better understand the physical mechanisms generating VLSMs and their variability as a consequence of the daily cycle of atmospheric stability, different topography and land cover; 2) explore how VLSMs affect downstream evolution of wakes produced by utility-scale wind turbines; 3) develop numerical tools that will enable thorough and timely predictions of wind turbine wakes by reproducing modulations of the Reynolds stresses induced by VLSMs. This research project is comprised of three interrelated tasks. First, there are two LIDAR measurement campaigns, the first one for a site over a relatively flat terrain in North Texas and a second one over a complex terrain. The third task uses the resulting experimental data for modeling VLSM-induced modulations on wind turbine wakes through optimal tuning of turbulence closure models within an adjoint Reynolds-averaged Navier-Stokes framework. This research project is helping to answer a number of key questions related to the morphology and energy content of VLSMs and how variable are they under different regimes of the atmospheric stability, the physical mechanisms governing generation of VLSMs and energy transport among coherent structures with different length-scales for ABL flows, and the role of land cover and topography in VLSM genesis and dynamics. The research project also aims to quantify the effects of the amplitude modulations induced by VLSMs on aerodynamic performance of utility-scale wind turbines and downstream evolution of wind turbine wakes.
