Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session G24: Energy: Wind Power Wakes, Control and Fluctuations I |
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Chair: Jhon Quinones, Purdue University Room: 150A |
Sunday, November 19, 2023 3:00PM - 3:13PM |
G24.00001: Parametric study of Coriolis effects on wind turbine wakes in a conventionally neutral atmospheric boundary layer Kirby S Heck, Michael F Howland Coriolis forces, which arise due to Earth's rotation, affect the structure of the atmospheric boundary layer (ABL). The structure of the ABL affects wind turbine wake dynamics indirectly, leading to effects such as wake skewing due to wind veer. Additionally, wakes are dynamically altered by Coriolis forces directly. This study uses large eddy simulations (LES) of a conventionally neutral ABL to explore the parametric dependence of direct and indirect effects of Coriolis forces on wake development. The Rossby number, which controls the strength of Coriolis forcing, is varied by changing the driving geostrophic wind speed. Time-averaged momentum budgets are analyzed to investigate wake evolution, focusing on the wake structure and recovery as a function of Coriolis forcing. In the streamwise direction, the effect of changing the Rossby number manifests primarily through indirect interactions with the ABL. As the strength of Coriolis forcing increases, the lateral momentum contributions are increasingly important, relative to the streamwise momentum. Net lateral advection depends parametrically on the Rossby number. Simplified LES experiments are used to parse the competing effects of pressure gradients, Reynolds stresses, and direct Coriolis forces in the lateral momentum balance. |
Sunday, November 19, 2023 3:13PM - 3:26PM |
G24.00002: Deficit budget analysis of turbulent wakes in the stratified atmospheric boundary layer Kerry S Klemmer, Michael F Howland As wind energy penetration increases, it becomes critically important to ensure that the modeling tools used for siting, design, and control of wind energy are robust to uncertainty. To model wind power, physics-based analytical wake models are typically used, which simplify atmospheric boundary layer (ABL) and wake physics. This is accomplished primarily through the parameterization of turbulence, thus introducing model-form uncertainty. In this study, we systematically analyze the physical mechanisms relevant to turbulence in the wakes of wind turbines operating in the stratified ABL. We use large eddy simulation (LES) to study wind turbine wakes under a variety of atmospheric stability conditions. To parse the turbulence in the wake from the turbulent, incident ABL flow, we decompose the flow into the base ABL flow and the deficit flow produced by the turbine. We then analyze the decomposed flow field budgets to study the effects of changing stability on important quantities in the wake, such as the momentum, mean kinetic energy, and turbulent kinetic energy. We perform this analysis with the goals of formulating new physics-based models that incorporate these important atmospheric effects and quantifying the impact of their omission. |
Sunday, November 19, 2023 3:26PM - 3:39PM |
G24.00003: Bispectral mode and scale analysis of wind turbine wake meandering Daniel Foti, Dinesh Kumar Kinjangi Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon, a coherent, dynamic, turbine-scale oscillation of the far wake. The effects of upwind scales on wake meandering are assessed by considering kinetic energy transfer between the dominant spatio-temporal scales. Triadic interactions, which are the mechanism of energy transfers between scales, manifests as a triple of wavenumbers or frequencies. The bispectrum is a function of two frequencies, which correlates the two frequencies to their sum, and identifies triads. A large-eddy simulation of a utility-scale wind turbine are used to acquire instantaneous velocity snapshots upwind and downwind of the turbine. A precursory simulation is employed to provide an inflow that contains a broad range of length-scales up to over an order of magnitude greater than the turbine diameter. Prominent upwind and downwind coherent structures, including upwind boundary layer scales, turbine rotor scales, and wake meandering are identified through two methods: bispectral mode decomposition and an energy transfer method based on triple decomposition and dynamic mode decomposition. The bispectrum from both methods is used to characterize the triadic interactions. |
Sunday, November 19, 2023 3:39PM - 3:52PM |
G24.00004: Influence of Upwind Length Scales on Wake Meandering Dinesh Kumar Kinjangi, Daniel Foti Wake meandering, a large-scale periodic transverse motion of the far wake of a wind turbine affects the overall variability in power production. Two distinct mechanisms have separately hypothesized its formation: (1) Large (much greater than the size of the diameter) upwind structures in the atmospheric boundary layer and (2) turbine-scale bluff body effects related to the size of the rotor. This study focuses on what ranges of upwind length scales interact with the turbine to affect wake meandering. We carry out a series of large-eddy simulations under a range of inflow scenarios to investigate how the distribution of upwind length scales changes the downwind spectra and spanwise velocity statistics. Initially, a precursory simulation of an atmospheric boundary layer is performed. The upwind length scale distribution is manipulated by a high by-pass filtering approach to produce four different upwind length scale scenarios with the largest length scale cutoff ranging from three times the boundary layer height to the turbine diameter. Wind turbine simulations for each scenario employ the actuator surface with the nacelle model to produce similar near-wake characteristics. The far wake exhibit differences to the instantaneous and averaged features of wake meandering. The comparison of the upwind to far wake power spectral densities shows that energy transfers between select length scales. |
Sunday, November 19, 2023 3:52PM - 4:05PM |
G24.00005: The Influence of Consecutive Gust on Turbine Under Yaw Misalignment Emmanuvel Joseph Aju, Pengyao Gong, Devesh Kumar, Rishi Sanjay Wale, Mario A Rotea, Yaqing Jin The sudden variation in wind speed, also known as gust, can increase the power output fluctuations and fatigue loading on wind turbines, as power output is proportional to the incoming velocity cubed and turbine loads are proportional to the incoming velocity squared. Extreme loads in gust events can also lead to significant and occasionally catastrophic damage to the turbine, such as tower strikes, in addition to fatigue failure from dynamic loads. This study focuses on how wake flows, power output fluctuations, and fluctuating aerodynamic loads on turbines under yaw misalignment in the presence of consecutive gust wind are fundamentally coupled. Systematic wind tunnel experiments were carried out with a model turbine to quantify the unsteady power outputs, thrust, and side-forces on turbines with varying yaw misalignment angles and incoming gust magnitude, and frequency. Furthermore, a reduced-order physical model was built based on local incoming flow statistics and turbine parameters to emphasize the dominant elements for modifying the variations of turbine power output and aerodynamic loads. |
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