Turbulent Structure of Canopy Flows using Large-Eddy Simulation: Homogeneous and Inhomogeneous Surfaces

使用大涡模拟的冠层流的湍流结构：均匀和非均匀表面

• 批准号: 0071377
• 负责人: Roger Shaw
• 金额: $ 30.91万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2004-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0071377&HistoricalAwards=false
• 关键词: Turbulent; Structure; Canopy; Flows; using

Turbulence accounts for the transport of heat, water vapor, CO2 and other quantities between the surface of the earth and the lower atmosphere. Plant and forest canopies have a strong effect on the wind flowing through them and hence modify the exchange processes. This project is a continuation of work on the distinctive flow patterns (coherent structures) that make a substantial contribution to the exchanges that take place between canopies and the surface layer. The strong velocity gradient at the interface between the canopy and the overlying layer of air induces a relatively high degree of organization to the turbulence, evidenced by strong velocity correlations, high velocity skewness, intermittency, and consistent and repeated flow patterns. Using the computational method of large-eddy simulation (LES), the main objectives of the work are:- Develop methods to visualize and examine the coherent patterns found in computed canopy flow fields.- Create descriptions of coherent structures by constructing a framework of the various elements of which the structures are composed.-Examine the vortex-like nature of the flow structures.- Perform simulations to examine the effects of inhomogeneous conditions, for example at forest edges.- Examine the statistical properties of the flow fields in such transition zones, and also the forces exerted on individual trees, to asses the potential for wind damage.By analyzing the physics of interactions between elements of the plant canopy (foliage, branches, and tree trunks) with the wind, the work provides a basis for explaining transport processes in the canopy.

湍流是热量、水蒸气、二氧化碳和其他物质在地球表面和低层大气之间的传输。植物和森林的树冠对流经它们的风有很大的影响，因此改变了交换过程。这个项目是对独特的流动模式(连贯结构)的继续工作，这种流动模式对树冠和表层之间发生的交换做出了重大贡献。冠层与上覆空气交界处的强速度梯度导致湍流具有较高的组织化程度，表现为强的速度相关性、高的速度偏斜性、间歇性以及一致和重复的流型。使用大涡模拟(LES)的计算方法，这项工作的主要目标是：-开发可视化和检查在计算的冠层流场中发现的相干模式的方法。-通过构建构成结构的各种元素的框架来创建相干结构的描述。-检查流动结构的涡状性质。-执行模拟以检查非均匀条件的影响，例如在森林边缘。-检查在这种过渡区中的流场的统计特性，以及施加在个别树木上的力，通过分析植物冠层元素(树叶、树枝和树干)与风相互作用的物理过程，这项工作为解释树冠内的运输过程提供了基础。