CAREER: A Universal Framework for Large-Eddy Simulation of Atmospheric Boundary Layer Flow Over Complex Terrain

职业生涯：复杂地形上大气边界层流大涡模拟的通用框架

• 批准号: 0645784
• 负责人: Fotini Chow
• 金额: $ 59.82万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0645784&HistoricalAwards=false
• 关键词: CAREER; Universal; Framework; Large; Eddy

The atmospheric boundary layer (ABL) directly influences human life through weather and air quality. Much remains to be understood about this thin atmospheric layer, partly because it is strongly affected by variations in topography and land-surface characteristics. These variations can lead to thermally-forced flow such as valley winds under calm conditions and atmospheric rotors and lee waves under strong winds with topographic blocking. Understanding the physical dynamics of such flow features requires detailed field observations and high-resolution numerical simulations. Large-eddy simulation (LES) is one of the most promising numerical techniques for modeling ABL flow because it allows control of turbulent length scales through spatial filtering to separate large, resolved motions from subfilter-scale, turbulent motions. Although primarily used for simulations of idealized flow conditions, LES has the potential to become universally applicable to ABL studies over complex terrain. Intellectual merit: This research will investigate key, innovative steps to extend the scalability of LES so it can be used from regional to very fine scales. This will allow LES to be effectively applied to flow over complex terrain and lead to greater insight into boundary layer flow processes. New strategies to control turbulent length scales, improve lateral boundary forcing, generate ensemble simulations, and reduce numerical errors due to subgrid surface roughness parameterizations and representation of steep topography will create a universal framework for general LES applications over complex terrain. This framework will be used together with observational data analysis to study terrain-induced flow features such as mountain waves and rotors and valley wind circulations. The PI has extensive prior experience with boundary layer flows over steep, mountainous terrain as well as with developing numerical methods and turbulence closure schemes for LES. An integrated education and outreach program is proposed to excite K-12 students and the general public about atmospheric boundary layer phenomena through an interactive modeling website and to provide numerical modeling experience to both undergraduate and graduate students. Students will participate in this public outreach program with UC Berkeley's Lawrence Hall of Science (LHS) through summer assistantships and a new graduate course on large-eddy simulation that will be directly coupled to the online exhibit. This course will also accelerate graduate research progress by providing hands-on training in numerical methods. Broader impacts: The proposed universal framework for LES will make possible seamless integration of flow features at all scales through nested simulations from the mesoscale to the urban scale. New knowledge of complex flows gained with this new numerical framework will dramatically improve models used to predict weather, air pollution, contaminant dispersion, and regional climate. Furthermore, insights into atmospheric circulations and intense gravity waves that can occur in mountainous areas will have important implications for aviation safety. New computational methods implemented in an advanced research numerical model will reach a broad community of users through continued public releases of code updates. Two graduate students will be trained through this research and two undergraduate research assistantships will be provided for under-represented minority engineering students through the SUPERB program at UC Berkeley. Research results will be disseminated through journal publications and conference presentations. The availability of the proposed educational tools will be advertised through the main Lawrence Hall of Science (LHS) website, through the PI's lab and department websites, and through an article in the Bulletin of the American Meteorological Society. The interactive modeling website has the potential to reach thousands of individuals and can be used in classroom settings at all age levels to introduce students to weather processes and numerical modeling. Hundreds of additional visitors, primarily K-12 students, will attend LHS museum floor demonstrations given by the PI and students.

大气边界层通过天气和空气质量直接影响人类的生活。关于这层薄薄的大气层，还有很多东西有待了解，部分原因是它受到地形和地表特征变化的强烈影响。这些变化可能导致热强迫流动，如平静条件下的谷风和地形阻塞强风下的大气转子和背风波。了解这些流动特征的物理动力学需要详细的现场观测和高分辨率的数值模拟。大涡模拟（LES）是模拟ABL流的最有前途的数值技术之一，因为它允许通过空间滤波来控制湍流长度尺度，以将大的、分辨的运动与子滤波尺度的湍流运动分离。虽然大涡模拟主要用于模拟理想化的流动条件，但它有可能普遍适用于复杂地形上的大气边界层研究。智力优点：这项研究将探讨关键的，创新的步骤，以扩大LES的可扩展性，使其可以用于从区域到非常精细的尺度。这将使LES有效地应用于复杂地形的流动，并导致更深入地了解边界层流动过程。新的策略来控制湍流的长度尺度，提高横向边界强迫，产生合奏模拟，并减少数值误差，由于亚网格表面粗糙度参数化和表示陡峭的地形将创建一个通用的框架，一般LES复杂地形的应用。该框架将与观测数据分析一起使用，以研究地形引起的流动特征，如山波和转子以及山谷风环流。PI在陡峭山区边界层流动以及开发LES的数值方法和湍流闭合方案方面具有丰富的经验。提出了一个综合的教育和推广计划，激发K-12学生和公众对大气边界层现象通过一个互动的建模网站，并提供数值模拟的经验，本科生和研究生。学生将通过暑期助教和一门新的大涡模拟研究生课程参与加州大学伯克利分校劳伦斯科学大厅（LHS）的公共宣传计划，该课程将直接与在线展览相结合。本课程还将通过提供数值方法的实践培训来加速研究生的研究进展。更广泛的影响：建议的通用框架LES将有可能无缝集成的流动功能在所有尺度上，通过嵌套模拟从中尺度到城市尺度。通过这种新的数值框架获得的复杂流动的新知识将大大改善用于预测天气、空气污染、污染物扩散和区域气候的模型。此外，深入了解山区可能发生的大气环流和强烈重力波将对航空安全产生重要影响。在高级研究数值模式中实施的新计算方法将通过持续公开发布代码更新来接触到广泛的用户社区。两名研究生将通过这项研究进行培训，两名本科生研究助学金将通过加州大学伯克利分校的SUPERB计划为代表性不足的少数民族工程专业学生提供。研究成果将通过期刊出版物和会议报告传播。拟议的教育工具的可用性将通过主要的劳伦斯科学大厅（LHS）网站，通过PI的实验室和部门网站，并通过在美国气象学会公报的文章进行宣传。交互式建模网站有可能接触到成千上万的人，并可用于所有年龄段的课堂设置，向学生介绍天气过程和数值建模。数百名额外的游客，主要是K-12学生，将参加由PI和学生提供的LHS博物馆地板演示。