Large-Eddy Simulation of Canopy and Surface Layer Flow

这项研究的目标是大气表层的大涡模拟(LES)，其中三维计算域的最低部分表示植物的副本，例如森林。植被由树叶元素密度、阻力系数和树冠内每个网格点的显热和水汽源或汇来表示。在大涡模拟中，网格网络分解的运动尺度直接以时间相关的形式计算，而亚网格尺度的过程是参数化的。我们的计划是利用模拟来研究植物树冠附近的湍流性质，并将该技术应用于更现实的(如不均匀的)情况。我们将对计算的流场中产生的相干结构进行深入的研究，并从开始到消散(这在现场是一项不可能完成的任务)。最初将使用小波和其他相关技术检测结构，并辅之以计算机动画。我们的目标是获得在低层大气和植物冠层之间的界面上发展的相干结构的尽可能完整的图像。适当的正交分解方法也将应用于计算的大涡模拟场。模型将包括植被和底层土壤的完整热能平衡，以更准确地引入土壤蒸发、蒸腾和土壤和生物量中的储热。还将介绍植物气动弹性特性的影响，并对Honami现象进行研究。为了表明我们在这方面的兴趣，我们已经开始研究防风林问题。所有计算都将在国家大气研究中心(NCAR)的Cray Y-MP上进行。

Shaw/Abstract The objective of this research is large-eddy simulation (LES) of the atmospheric surface layer in which the lowest portion of the three-dimensional computational domain represents a plant copy such as a forest. The vegetation is represented by a foliage element are density, a drag coefficient, and a sensible heat and water vapor source or sink at each grid point within the canopy. In the LES, scales of motion resolved by the grid network are computed directly in time-dependent form, while sub-grid-scale processes are parameterized. Our plan is to use the simulations to study the nature of turbulence in the vicinity of plant canopies, and to apply the technique to more realistic (such as inhomogeneous) situations. We will perform in-depth studies of coherent structures created within the computed flow fields and follow them from inception to dissipation (an impossible task in the field). Structures will initially be detected using wavelet and other related techniques, complemented by computer animation. It is our aim to obtain as complete a picture as possible of coherent structures developing at the interface between the lower atmosphere and a plant canopy. The method of proper orthogonal decomposition will also be applied to computed LES fields. A complete thermal energy balance of the vegetation and of the underlying soil will be incorporated into the model to more correctly introduce soil evaporation, transpiration, and heat storage in both soil and biomass. The influence of aeroelastic properties of the vegetation will also be introduced and a study made of the phenomenon of honami. As a demonstration of our interests in this regard, we have begun an examination of the windbreak problem. All computation will be performed on the Cray Y-MP at the National Center for Atmospheric Research (NCAR).