Collaborative Research: Explicit filtering and adaptive mesh refinement for large-eddy simulation

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。大涡模拟（LES）是模拟复杂湍流的一种最有前途的数值技术，在从工程到地球物理流动的各种应用中都有应用。今天，在这种应用中广泛使用LES的主要障碍之一是缺乏有效适应复杂边界条件的高精度数值技术。结合浸入边界法的结构化自适应网格细化（S-AMR）求解器的出现为LES提供了新的机遇，因为它们可以适应复杂的边界条件，有效地分布计算节点，同时保持结构化求解器的大部分特征。然而，结合S-AMR/LES方法，需要开发能够处理自适应网格固有的复杂性和灵活性的滤波和建模策略。本研究旨在克服这些挑战，并通过开发和测试显式滤波和重建方法，使LES成为一个强大的模拟工具，用于大范围的实际应用，这些方法允许湍流波动在S-AMR中精确地穿过粗-细网格界面。先前的尝试显示出比传统结果有显著改善。这些发展将很容易转移到各自研究界的现有规范中。此外，这些发展将改变LES在工程和地球物理中的应用，通过改进湍流建模的基本方面，并使复杂几何形状的流动模拟成为可能，这在以前是不可能的，因为高数值误差和高计算成本。本研究中特别关注的应用将使粗壁边界层的新物理发现成为可能，并为城市环境中大气污染物扩散计算的准确性/效率设定新的标准。除研究生外，该项目还将支持加州大学伯克利分校的博士后研究人员一年。通过与两位个人导师的互动，将提供职业咨询和助学金写作培训。学生课堂项目将帮助创建一个公共互动网站，以升级维基百科中关于LES和自适应网格细化的当前页面。Wiki网站将有助于传播对LES作为通用模拟工具的局限性和巨大潜力的理解。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). 0933642/0932613 Chow/BalarasLarge-eddy simulation (LES) is one of the most promising numerical techniques for modeling complex turbulent flows in a variety of applications ranging from engineering to geophysical flows. Today, one of the main obstacles to the widespread use of LES for such applications is the lack of high-accuracy numerical techniques that efficiently accommodate complex boundary conditions. The advent of structured adaptive mesh refinement (S-AMR) solvers combined with immersed boundary methods offers new opportunities for LES since they can accommodate complex boundary conditions, efficiently distribute computational nodes and at the same time maintain most of the features of structured solvers. A combined S-AMR/LES approach, however, requires the development of filtering and modeling strategies that can deal with the complexity and flexibility inherent to adaptive grids. This study seeks to overcome these challenges and make LES a robust simulation tool for a large range of practical applications, by developing and testing explicit filtering and reconstruction approaches that allow turbulent fluctuations to accurately cross coarse-fine grid interfaces in S-AMR. Previous attempts showed significant improvement over traditional results. These developments will be easily transferrable to existing codes of respective research communities. In addition, these developments will transform LES use in engineering and geophysics by improving fundamental aspects of turbulence modeling and enabling the simulation of flow in complex geometries that were never before possible due to high numerical errors and high computational cost. The particular focus applications in this study will enable the discovery of new physics of rough-wall boundary layers and set new standards for accuracy/efficiency in computations of atmospheric contaminant dispersion in urban environments. In addition to graduate students, this project will support a postdoctoral researcherat UC Berkeley for one year. Career counseling and grant writing training will be provided through interactions with both PIs. Student class projects will help create a public interactive website to upgrade the current pages in Wikipedia on LES and adaptive mesh refinement. The Wiki websites will aid in spreading nderstanding of the limitations but also of the great potential of LES as a universal simulation tool.