基于激光雷达测风数据的复杂地形下风力机尾流特性研究

以张家口某处风电场为实验场地,采用两台多普勒激光雷达(Wind3D 6000和WindMast WP350)分别测量风力机的尾流和来流风速,对全尾流、半尾流和独立尾流3种工况进行研究。结果表明,3种工况下随着尾流发展尾流宽度均不断变大,而尾流深度和速度衰减则不断减小;全尾流和半尾流工况中,上游风力机的存在会增加下游风力机尾流宽度,且全尾流比半尾流的增加量大;全尾流和半尾流工况中,相较于上游风力机,下游风力机尾流深度和速度衰减均较小。     

三维山体过山气流流场特征的数值模拟

采用高阶矩湍流闭合方案，建立了一个细网格、高分辨率、三维非静力ＰＢＬ数值模式，并由其模拟了三维山体条件下的流场结构和湍流场特征。为反映数值模拟结果的可靠性，对中性条件下三维山体流场进行了风洞试验。与数值模拟结果对比分析表明，数值计算与风洞试验结果有较好的一致性；使用该模式模拟山体条件下的流场结构能取得较好的结果；将模拟结果作为随机游动扩散模式的三维风场及湍流场资料输入，为复杂地形条件下大气污染的研     

大型风电场群风电场布局间距的模型研究

利用边界层理论和梯度输送原理,依据动量守恒定律,在大气中性层结条件下建立了风电场的动量吸收模型和风电场下游的动量补偿模型,计算出风电场尾流距离。参照实际风电场布局规模和风机几何参数设计数值试验,并对尾流距离与这些参量之间的关系进行了初步分析。结果表明,风电场尾流距离随风机直径、风塔高度、风机行数和风机动能利用系数的增加而增大,随地表粗糙度和风机列间距的增加而减小,并且这一距离不受风速和风机列数的影响。     

城市中水体布局对大气环境的影响

城市下垫面状况在很大程度上决定城市大气物理环境的特征。在城市区域增加湿地等自然地表有利于城市的减温增湿,促使局地流场发生变化,改善局地微气象条件以及大气物理环境。城市规划大气物理环境多尺度数值模拟系统为城市规划大气物理环境定量评估提供了有效的模拟工具。利用该系统中的城市尺度模式模拟了水体布局为集中型和分散型,水体面积占有率分别为4%、8%、12%和16%条件下,城市大气温度、湿度、风速、城市大气扩散条件的变化及其对城市大气环境的影响,利用北京市城市水体气象观测数据,分析了水体周边和商业区、交通区温、湿度的差异,并对模式模拟结果进行了验证,揭示了城市水体布局对城市大气物理环境影响的可能机制。模拟和观测结果显示,城市水体布局会对城市微气象环境产生一定影响。无论分散型或集中型布局,城市水体面积的增加,都在一定程度上使城市气温降低、湿度增加、平均风速增大。比较而言,分散型水体布局对城市区域微气象环境的影响更为显著。     

复杂下垫面风电场风速数值模拟及误差特征

利用WRF模式分别对沿海及山地条件下风电场风速进行高分辨数值模拟,并对其误差特征进行分析,结果表明:1)WRF模式对复杂地形条件下的风速模拟性能良好,模拟值较好地体现天气尺度的周期变化;2)沿海及山地条件下模拟与观测的误差特征各不相同。模式静态数据未能显现沿海的小岛,并且低估了山地测风塔所在的海拔,导致沿海平均模拟风速偏大,山地平均模拟风速偏小;3)分析不同风向的归一化均方根误差,沿海陆风情况下,下垫面相对复杂,误差明显增大;沿海海风情况下,下垫面均一,误差明显减小;4)仅作单个风电场周边数百平方千米的模拟,采用一台12核的服务器进行WRF模式的并行计算可满足48 h短期预测的时效性。仅仅提高模拟的网格分辨率,并不一定能提升模拟的准确性。     

辽宁风车田选址方法研究及应用

1 风车田选址的技术条件及对策风车田也称风电场,它将多台(几十直至几百台)风力机集中摆放某一有利地区,是大规模开发利用风能的一种形式.因此,风车田的选址应根据风能资源调查与区划的结果,选择有利     

近20年来风电场（群）对气候的影响研究进展

随着风电场的大规模开发,其对气候的影响受到关注,自2000年以来美国和欧洲等国陆续开展了一定的研究,中国也开展了一些观测和模拟研究,对已有研究进行综述可指导这项工作的进一步开展。通过对文献的梳理,总结了风电场对气候影响的研究进程、研究方法、影响机理和研究成果。大量观测和数值模拟结果显示风电场会导致地表气温上升,风电场下游一定距离范围内风速衰减,并间接影响降水、蒸发等其他气象要素,风电场对局地气候变化产生影响的结论具有较高信度;部分模式模拟结果显示未来大规模风电场（群）开发对全球气候也有可能产生一定影响,但仍需进一步的探索。     

壁面局部粗糙对大涡结构作用的非线性演化研究

在构建大涡结构理论模型的基础上,采用局部喷入和吸出的结构来模拟局部粗糙壁面诱导的感应扰动场,数值研究局部粗糙对大涡结构之间非线性作用的影响问题。数值结果表明,局部粗糙壁面诱导的感应扰动改变了原平均速度剖面的稳定性特性及感应扰动流场的三维性对激励大涡结构的快速增长起了关键性的作用。     

风电场对气候变化影响研究进展

综述了国际评估风电场对局地和全球气候变化的短期和较长期的可能影响,并且将其影响与人类排放的影响作简单的对比.大量的观测和数值模拟研究表明,风电场的运行明显减小下游风速,同时随局地近地层稳定度的不同也造成下游温度明显上升或下降.一些数值模拟研究表明,如果全球建立大量大型风电场,例如假定全球使用风能占总能源10％以上,即全...     

基于GIS的陕西风电场微地形选址技术研究

以陕西已建成的风电场区域为对象,通过对其数字高程模型(Digital Elevation Model,简称DEM)进行宏观和微观的数字地形分析,了解其不同地形因子的数字分布阈值,确定满足风电场建设的地形因子条件;再结合风能资源数值模拟结果,形成风电场微地形选址的重要条件;通过该条件对全省1∶25万DEM进行网格式搜索,最终形成全省风电场选址建设区划图。     

Turbulent Flow Properties Around a Staggered Wind Farm

The fundamental properties of turbulent flow around a perfectly staggered wind farm are investigated in a wind tunnel. The wind farm consisted of a series of 10 rows by 2–3 columns of miniature wind turbines spaced 5 and 4 rotor diameters in the streamwise and spanwise directions respectively. It was placed in a boundary-layer flow developed over a smooth surface under thermally neutral conditions. Cross-wire anemometry was used to obtain high resolution measurements of streamwise and vertical velocity components at various locations within and above the wind farm. The results show that the staggered configuration is more efficient in terms of momentum transfer from the background flow to the turbines compared to the case of an aligned wind turbine array under similar turbine separations in the streamwise and spanwise directions. This leads to improved power output of the overall wind farm. A simplified analysis suggests that the difference in power output between the two configurations is on the order of 10%. The maximum levels of turbulence intensity in the staggered wind farm were found to be very similar to that observed in the wake of a single wind turbine, differing substantially with that observed in an aligned configuration with similar spacing. The dramatic changes in momentum and turbulence characteristics in the two configurations show the importance of turbine layout in engineering design. Lateral homogenization of the turbulence statistics above the wind farm allows for the development of simple parametrizations for the adjustment of flow properties, similar to the case of a surface roughness transition. The development of an internal boundary layer was observed at the upper edge of the wind farm within which the flow statistics are affected by the superposition of the ambient flow and the flow disturbance induced by the wind turbines. The adjustment of the flow in this layer is much slower in the staggered situation (with respect to its aligned counterpart), implying a change in the momentum/power available at turbine locations. Additionally, power spectra of the streamwise and vertical velocity components indicate that the signature of each turbine-tip vortex structure persists to locations deep within the wind farm.     

Simulation of Turbulent Flow Inside and Above Wind Farms: Model Validation and Layout Effects

A recently-developed large-eddy simulation framework is validated and used to investigate turbulent flow within and above wind farms under neutral conditions. Two different layouts are considered, consisting of thirty wind turbines occupying the same total area and arranged in aligned and staggered configurations, respectively. The subgrid-scale (SGS) turbulent stress is parametrized using a tuning-free Lagrangian scale-dependent dynamic SGS model. The turbine-induced forces are modelled using two types of actuator-disk models: (a) the ‘standard’ actuator-disk model (ADM-NR), which calculates only the thrust force based on one-dimensional momentum theory and distributes it uniformly over the rotor area; and (b) the actuator-disk model with rotation (ADM-R), which uses blade-element momentum theory to calculate the lift and drag forces (that produce both thrust and rotation), and distributes them over the rotor disk based on the local blade and flow characteristics. Validation is performed by comparing simulation results with turbulence measurements collected with hot-wire anemometry inside and above an aligned model wind farm placed in a boundary-layer wind tunnel. In general, the ADM-R model yields improved predictions compared with the ADM-NR in the wakes of all the wind turbines, where including turbine-induced flow rotation and accounting for the non-uniformity of the turbine-induced forces in the ADM-R appear to be important. Another advantage of the ADM-R model is that, unlike the ADM-NR, it does not require a priori specification of the thrust coefficient (which varies within a wind farm). Finally, comparison of simulations of flow through both aligned and staggered wind farms shows important effects of farm layout on the flow structure and wind-turbine performance. For the limited-size wind farms considered in this study, the lateral interaction between cumulated wakes is stronger in the staggered case, which results in a farm wake that is more homogeneous in the spanwise direction, thus resembling more an internal boundary layer. Inside the staggered farm, the relatively longer separation between consecutive downwind turbines allows the wakes to recover more, exposing the turbines to higher local wind speeds (leading to higher turbine efficiency) and lower turbulence intensity levels (leading to lower fatigue loads), compared with the aligned farm. Above the wind farms, the area-averaged velocity profile is found to be logarithmic, with an effective wind-farm aerodynamic roughness that is larger for the staggered case.     

基于风速高相关分区的风电场风速预报订正

为了提高风电场风速预报和功率预测的精度和准确率,并考虑风机测风数据的不稳定因素,以多年服务的内蒙古中部某风力发电场A为研究区,在勘察风电场地形及风机布局后,按照季节、风向进行风机间风速时空相关性分析,划分出风机轮毂高度风速高相关为典型特征的风机网格分类片区,采用卡尔曼滤波方法,通过直接和间接两种订正方案,分别进行风机片区风速订正。结果表明:风速高相关风机片区的划分,对于提高风电场风速预报及功率预测精度和准确率具有一定作用,利用风电场区测风塔梯度观测风速,对风机片区进行间接订正,可有效改善数值模式预报风速,15个片区类型下相关系数由0.18~0.72提高至0.67~0.91,误差绝对值由1.6~2.9 m·s-1降低至1.0~1.5 m·s-1。     

A Numerical Study of Wind-Turbine Wakes for Three Atmospheric Stability Conditions

The effects of atmospheric stability on wind-turbine wakes are studied via large-eddy simulations. Three stability conditions are considered: stable, neutral, and unstable, with the same geostrophic wind speed aloft and the same Coriolis frequency. Both a single 5-MW turbine and a wind farm of five turbines are studied. The single-turbine wake is strongly correlated with stability, in terms of velocity deficit, turbulence kinetic energy (TKE) and temperature distribution. Because of the Coriolis effect, the wake shape deviates from a Gaussian distribution. For the wind-farm simulations, the separation of the core region and outer region is clear for the stable and neutral cases, but less distinct for the unstable case. The unstable case exhibits strong horizontal variations in wind speed. Local accelerations such as related to aisle jets are also observed, whose features depend on stability. The added TKE in the wind farm increases with stability. The highest power extraction and lowest power deficit are observed for the unstable case.     

Performance of the Wind Farm Parameterization Scheme Coupled with the Weather Research and Forecasting Model under Multiple Resolution Regimes for Simulating an Onshore Wind Farm

We use the Wind Farm Parameterization(WFP) scheme coupled with the Weather Research and Forecasting model under multiple resolution regimes to simulate turbulent wake dynamics generated by a real onshore wind farm and their influence at the local meteorological scale. The model outputs are compared with earlier modeling and observation studies. It is found that higher vertical and horizontal resolutions have great impacts on the simulated wake flow dynamics. The corresponding wind speed deficit and turbulent kinetic energy results match well with previous studies. In addition, the effect of horizontal resolution on near-surface meteorology is significantly higher than that of vertical resolution. The wake flow field extends from the start of the wind farm to downstream within 10 km, where the wind speed deficit may exceed 4%. For a height of 150 m or at a distance of about 25 km downstream, the wind speed deficit is around 2%. This indicates that, at a distance of more than 25 km downstream, the impact of the wind turbines can be ignored. Analysis of near-surface meteorology indicates a night and early morning warming near the surface, and increase in near-surface water vapor mixing ratio with decreasing surface sensible and latent heat fluxes. During daytime, a slight cooling near the surface and decrease in the near-surface water vapor mixing ratio with increasing surface sensible and latent heat fluxes is noticed over the wind farm area.     

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Wind-turbine-wake evolution during the evening transition introduces variability to wind-farm power production at a time of day typically characterized by high electricity demand. During the evening transition, the atmosphere evolves from an unstable to a stable regime, and vertical stratification of the wind profile develops as the residual planetary boundary layer decouples from the surface layer. The evolution of wind-turbine wakes during the evening transition is examined from two perspectives: wake observations from single turbines, and simulations of multiple turbine wakes using the mesoscale Weather Research and Forecasting (WRF) model. Throughout the evening transition, the wake’s wind-speed deficit and turbulence enhancement are confined within the rotor layer when the atmospheric stability changes from unstable to stable. The height variations of maximum upwind-downwind differences of wind speed and turbulence intensity gradually decrease during the evening transition. After verifying the WRF-model-simulated upwind wind speed, wind direction and turbulent kinetic energy profiles with observations, the wind-farm-scale wake evolution during the evening transition is investigated using the WRF-model wind-farm parametrization scheme. As the evening progresses, due to the presence of the wind farm, the modelled hub-height wind-speed deficit monotonically increases, the relative turbulence enhancement at hub height grows by 50%, and the downwind surface sensible heat flux increases, reducing surface cooling. Overall, the intensifying wakes from upwind turbines respond to the evolving atmospheric boundary layer during the evening transition, and undermine the power production of downwind turbines in the evening.     

Effects of Thermal Stability and Incoming Boundary-Layer Flow Characteristics on Wind-Turbine Wakes: A Wind-Tunnel Study

Wind-tunnel experiments were carried out to study turbulence statistics in the wake of a model wind turbine placed in a boundary-layer flow under both neutral and stably stratified conditions. High-resolution velocity and temperature measurements, obtained using a customized triple wire (cross-wire and cold wire) anemometer, were used to characterize the mean velocity, turbulence intensity, turbulent fluxes, and spectra at different locations in the wake. The effect of the wake on the turbulence statistics is found to extend as far as 20 rotor diameters downwind of the turbine. The velocity deficit has a nearly axisymmetric shape, which can be approximated by a Gaussian distribution and a power-law decay with distance. This decay in the near-wake region is found to be faster in the stable case. Turbulence intensity distribution is clearly non-axisymmetric due to the non-uniform distribution of the incoming velocity in the boundary layer. In the neutral case, the maximum turbulence intensity is located above the hub height, around the rotor tip location and at a distance of about 4–5.5 rotor diameters, which are common separations between wind turbines in wind farms. The enhancement of turbulence intensity is associated with strong shear and turbulent kinetic energy production in that region. In the stable case, the stronger shear in the incoming flow leads to a slightly stronger and larger region of enhanced turbulence intensity, which extends between 3 and 6 rotor diameters downwind of the turbine location. Power spectra of the streamwise and vertical velocities show a strong signature of the turbine blade tip vortices at the top tip height up to a distance of about 1–2 rotor diameters. This spectral signature is stronger in the vertical velocity component. At longer downwind distances, tip vortices are not evident and the von Kármán formulation agrees well with the measured velocity spectra.     

Increasing the Power Production of Vertical-Axis Wind-Turbine Farms Using Synergistic Clustering

Vertical-axis wind turbines (VAWTs) are being reconsidered as a complementary technology to the more widely used horizontal-axis wind turbines (HAWTs) due to their unique suitability for offshore deployments. In addition, field experiments have confirmed that vertical-axis wind turbines can interact synergistically to enhance the total power production when placed in close proximity. Here, we use an actuator line model in a large-eddy simulation to test novel VAWT farm configurations that exploit these synergistic interactions. We first design clusters with three turbines each that preserve the omni-directionality of vertical-axis wind turbines, and optimize the distance between the clustered turbines. We then configure farms based on clusters, rather than individual turbines. The simulations confirm that vertical-axis wind turbines have a positive influence on each other when packed in well-designed clusters: such configurations increase the power generation of a single turbine by about 10 percent. In addition, the cluster designs allow for closer turbine spacing resulting in about three times the number of turbines for a given land area compared to conventional configurations. Therefore, both the turbine and wind-farm efficiencies are improved, leading to a significant increase in the density of power production per unit land area.     

Impact of Neutral Boundary-Layer Turbulence on Wind-Turbine Wakes: A Numerical Modelling Study

The wake characteristics of a wind turbine in a turbulent boundary layer under neutral stratification are investigated systematically by means of large-eddy simulations. A methodology to maintain the turbulence of the background flow for simulations with open horizontal boundaries, without the necessity of the permanent import of turbulence data from a precursor simulation, was implemented in the geophysical flow solver EULAG. These requirements are fulfilled by applying the spectral energy distribution of a neutral boundary layer in the wind-turbine simulations. A detailed analysis of the wake response towards different turbulence levels of the background flow results in a more rapid recovery of the wake for a higher level of turbulence. A modified version of the Rankine–Froude actuator disc model and the blade element momentum method are tested as wind-turbine parametrizations resulting in a strong dependence of the near-wake wind field on the parametrization, whereas the far-wake flow is fairly insensitive to it. The wake characteristics are influenced by the two considered airfoils in the blade element momentum method up to a streamwise distance of 14D (D = rotor diameter). In addition, the swirl induced by the rotation has an impact on the velocity field of the wind turbine even in the far wake. Further, a wake response study reveals a considerable effect of different subgrid-scale closure models on the streamwise turbulent intensity.