Dynamics of macro-vortices in horizontal axis turbine wind farms

众所周知，流体动力学和湍流现象在风力发电场的性能、效率和环境影响中起着主导作用。人们越来越有兴趣利用流体动力学知识来改进风能收集，从而实现诸如减少温室气体排放和可再生能源经济等社会效益。该研究项目旨在开发用于风力发电厂设计和控制的气流模型。工作假设是，由涡轮运动引起的流动改变，如调整涡轮转子对流入气流的角度（偏转或倾斜）或调节功率提取的表面脉冲，可以最好地利用被称为“宏观涡旋”的超大旋涡流结构模型来理解。据信，在风力发电厂的涡轮机下游，这样的涡流可以延伸数百米。这些结构可以负责改变风速、方向和风力的频率，并影响下游涡轮机的性能。本研究计划将使用电脑模拟来研究湍流中大尺度涡旋的产生、演化及衰减。教育和外展活动将通过约翰霍普金斯大学女工程师协会利用国家和国际研究网络。K-12的推广将通过约翰霍普金斯大学的教育推广中心进行协调，并将包括作为高中生暑期项目“工程创新”一部分的讲座。项目研究人员还将参加当地一所小学的课间活动。该研究项目将开发利用风力涡轮机偏航、倾斜和循环来利用大规模流动驱动潜力所需的基础知识，以提高风力发电场的性能。各种研究问题将使用来自一套大涡模拟（LES）的偏航，倾斜和周期性强迫涡轮机的高保真数值数据集来解决。该项目将描述在各种条件下产生的宏观涡旋的特性（强度、有效核心大小、位置和轨迹），包括剪切、表面粗糙度和大气的热分层，例如在浮力（白天）和稳定分层（夜间）条件下。该项目将开发简化模型，利用从各种LES数据中吸取的教训，以及从涡度动力学的基本物理和简化描述（如升力线理论）中吸取的教训。由此产生的简化模型和LES见解将用于寻找宏观漩涡的改进安排或最佳网络。目标是增加平均动能的垂直夹带，从风力涡轮机上方的较快风向下进入风力涡轮机区域。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Fluid dynamics and turbulent flow phenomena are known to play dominant roles in the performance, efficiency and environmental impact of wind farms. There is growing interest in using fluid dynamics knowledge to improve wind energy harvesting and thereby achieve societal benefits such as reduced greenhouse gas emissions and a renewable energy economy. This research project aims to develop air flow models for use in wind plant design and control. The working hypothesis is that flow modifications resulting from turbine actions, such as adjusting the angle of the turbine rotor to the incoming flow (yawing or tilting) or pulsing the surfaces that regulate power extraction, can best be understood using models of very large swirling flow structures called "macro-vortices." Such vortices are believed to extend for many hundreds of meters downstream of turbines in a wind farm. These structures can be responsible for changing the speed, direction, and frequency of the wind exiting a turbine and impacting the performance of downstream turbines. This research project will use computer simulations to study the generation, evolution, and decay of large-scale vortices in turbulent flows. Educational and outreach activities will leverage national and international research networks through Johns Hopkins University Society of Women Engineers. K-12 outreach will be coordinated through the Center for Educational Outreach at Johns Hopkins University and will include lectures as part of Engineering Innovation, a summer program for high school students. The project researchers will also participate in an intersession program at a local elementary school.This research project will develop the fundamental knowledge required to harness the potential of large-scale flow actuation, using wind turbine yaw, tilt, and cycling, in order to improve wind farm performance. Various research questions will be addressed using high-fidelity numerical datasets from a suite of Large Eddy Simulations (LES) of yawed, tilted, and periodically forced turbines. The project will characterize the properties (strength, effective core-size, positions and trajectories) of the macro-vortices generated under various conditions, including shear, surface roughness, and thermal stratification of the atmosphere, e.g. under buoyant (daytime) and stably stratified (nighttime) conditions. The project will develop reduced models that leverage lessons learned from the various LES data, as well as from basic physics of vorticity dynamics and simplified descriptions such as lifting line theory. The resulting reduced models and LES insights will be used to find improved arrangements or optimal networks of macro-vortices. The objective would be to increase vertical entrainment of mean kinetic energy from the faster winds above the wind turbines down into the wind turbine region.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.