Bulletin of the American Physical Society
73rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 65, Number 13
Sunday–Tuesday, November 22–24, 2020; Virtual, CT (Chicago time)
Session Q07: Boundary Layers: Wind Turbine Interaction (3:55pm - 4:40pm CST)Interactive On Demand
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Q07.00001: Using flow visualization with natural snowfall to quantify the effects of atmospheric coherent structures on a utility-scale wind turbine Aliza Abraham, Jiarong Hong The presence of coherent structures in atmospheric turbulence can lead to substantial changes in the structural loading, power generation, and wake behaviors of utility-scale wind turbines. These structures are difficult to model in the laboratory or in simulations, and their effects on turbine operation have not been well understood due to limitations in field measurement techniques. In the current study, flow visualization and super-large-scale particle image velocimetry using natural snowfall were employed to quantify the impact of these coherent turbulent structures on turbine loading, operation, and wake. Three datasets with fields-of-view capturing the inflow and wake simultaneously were recorded, with significantly different levels of turbulence depending on the mean wind speed. In all datasets, structural loading increased with the presence of inflow coherent structures, though the correlation strength varied with turbine operational regime. Further, these structures were found to reduce power output at low wind speeds. Finally, the strong influence of these structures on tip vortex behavior in the near wake was also observed. These effects demonstrate the need to improve the accuracy of turbulence modelling in simulations of turbine-atmosphere interactions. [Preview Abstract] |
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Q07.00002: Investigating Blockage Effects in Large-scale Wind Farms Using Large Eddy Simulations Jessica Strickland, Richard Stevens Flow blockage can alter the performance of closely-spaced wind turbines as they obstruct incoming air flow. Unfortunately, this phenomenon is relatively under-researched and not yet incorporated into widely-used wind farm models. Some studies have shown that tightly-packed turbines can benefit from each other while others claim that blockage hinders the performance of large wind farms. Here, we use large eddy simulations (LES) to analyse an encompassing set of turbine array configurations in realistic neutral boundary layer conditions. We compare a stand-alone turbine, an infinite row of turbines, and a wind farm with eight rows, focusing primarily on how the blockage depends on the spanwise and streamwise turbine spacing. Our results show that different physical mechanisms play a role. The turbines appear to benefit from close, spanwise neighbours as the flow that is obstructed by one turbine is then diverted into the rotor area of another turbine, increasing its power production. In contrast, close streamwise turbines negatively impact the power output of upstream turbines as the flow is inclined to pass over the wind farm. In addition, we find that these blockage effects do not depend on the atmospheric turbulence intensity. [Preview Abstract] |
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Q07.00003: Exploring the Effects of Low-Level-Jet Velocity Profiles on the Energy Entrainment of Vertical-Axis Wind Turbines Diego Siguenza, Ali Doosttalab, Shyuan Cheng, Humberto Bocanegra-Evans, Leanordo P. Chamorro, Luciano Castillo The velocity peaks created by atmospheric low-level jets results in attractive power resource for wind turbines. We experimentally explored the effects of a series of low-level-jet velocity profiles on the energy entrainment in the wakes of a single and a pair of counter-rotating vertical-axis wind turbine models using particle image velocimetry in a wind tunnel. Results show that the positive shear region of the velocity profiles increases the wake asymmetry due to higher vertical velocity gradients. It is also shown that the LLJ velocity profile improves the wake energy entrainment in comparison with standard boundary layer profiles by increasing the mean kinetic energy advection into the wake. [Preview Abstract] |
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Q07.00004: An Experimental Survey on the Interaction of Wind Turbines over Complex Terrain Diego Siguenza-Alvarado, Ali Doosttalab, Leonardo P. Chamorro, Luciano Castillo Wind turbines sited at the top of hills benefit from the speed-up effect, relatively lower turbulence, and less significant wake influence of upstream turbines in comparison with flat terrains. In this work, we use particle image velocimetry measurements in a wind-tunnel to reveal the wake characteristics of different turbine arrays in the windward side of a 2D steep-hill. We also measure the model's power and dynamic responses, and we study its relation with the wake's turbulence statistics. The results here presented can be used for wind turbines layout optimization in complex terrains. [Preview Abstract] |
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Q07.00005: Spectral analysis of flow, wind turbine and wake interaction in low-level jet conditions Ali Doosttalab, Humberto Bocanegra Evans, Diego Siguenza-Alvarado, Shyuan Cheng, Leonardo Chamorro, Luciano Castillo The low-level jet (LLJ) is an atmospheric phenomenon characterized by relatively low-tropospheric maximum in the vertical profile of the horizontal winds which may offer an attractive power resource for wind turbines. Here, we present laboratory measurements of the velocity field and power spectral analysis of model wind turbines operating in a synthetic low-level jet. Our results reveal a large peak in the velocity spectra that arises from the interaction of the LLJ velocity peak and the tip of the rotor, which creates a strong shear layer. Although this shear layer does not have a significant effect on the spectrum of the generated power, the induced large scale velocity fluctuations may produce structural loading in wind turbines within wind farms. [Preview Abstract] |
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Q07.00006: Multi-faceted Wind Turbine Siting and Resource Characterization Over Complex Terrains Abigayle Moser, Diego Siguenza-Alvarado, Ali Doosttalab, Luciano Castillo Power transmission across vast expanses remains a major barrier in providing energy security to underserved regions. Renewable energy sources such as wind and solar power are unique solutions to solve imbalances and connectivity in hard-to-reach areas. This study seeks to outline a framework for resource characterization and wind farm implementation in isolated regions through meteorological assessments coupled with experimental data. Wind turbine siting criteria includes integrating atmospheric dynamics with existing and hypothetical wind farm locations to evaluate their performance. A fusion of meteorological data and satellite imagery were used to assess wind turbine siting based on wind and solar resource availability. In order to examine the effect of complex terrains on wind power production, wind tunnel experiments were performed with a scaled-down model wind farm. Computational fluid dynamics (CFD) simulations were performed to validate the experimental data and investigate wind-farm wake interaction with complex topographies. The results from the modeled wind farm demonstrate the role of high-gradient topographic slopes on wind-farm power output and wake recovery by means of energy entrainment. [Preview Abstract] |
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Q07.00007: Effect of wind turbines and atmospheric stability on turbulent boundary layers Marco Placidi, Philip Hancock, Paul Hayden Wind power is becoming an ever-more significant contributor to the overall energy production across the globe as the net benefits of renewable energy and the advantage of economy of scale become clearer. In this climate, it is therefore important to gain a deeper understanding and more accurate predictability of the wind power availability. Simple but effective methods (e.g. Veers, Report SAND83-1909,1984) rely on information on the incoming turbulence correlations across the turbine's rotor (amongst other quantities). These correlations, however, vary greatly with (i) the presence of upstream turbines, and (ii) the atmospheric conditions. To investigate the effect of these on wind turbine performance, experiments were carried out in the EnFlo wind tunnel at Surrey in both neutrally and weakly thermally stratified boundary layers (with and without an overlying inversion). Both a single rotor in isolation and two aligned turbines were considered. The model turbines are 1:300 scaled replicas of a typical 5MW turbine for off-shore application. The presentation will cover the effect of atmospheric stability and the presence of upstream wind turbines on turbulence statistics and characteristic lengthscales. [Preview Abstract] |
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