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

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)提供资金的。0933642/0932613 Chow/Balaras大涡模拟(LES)是模拟复杂湍流的最有前途的数值技术之一，其应用范围从工程应用到地球物理流动。今天，大涡模拟广泛应用的主要障碍之一是缺乏能够有效适应复杂边界条件的高精度数值技术。结构自适应网格加密与浸没边界方法相结合的出现为大涡模拟提供了新的机会，因为它们可以适应复杂的边界条件，有效地分布计算节点，同时保持了结构求解器的大部分特征。然而，S-AMR/LES组合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过滤和建模策略。这项研究旨在克服这些挑战，使大涡模拟成为一个强大的模拟工具，广泛的实际应用，通过开发和测试显式的过滤和重建方法，允许湍流涨落准确地穿过S-AMR的粗-细网格界面。之前的尝试显示，与传统结果相比，情况有了显著改善。这些发展将很容易被转移到各自研究社区的现有代码中。此外，这些发展将改变大涡模拟在工程和地球物理中的使用，改进湍流建模的基本方面，并使复杂几何中的流动模拟成为可能，而这是以前由于高数值误差和高计算成本而无法实现的。这项研究中特别重点的应用将有助于发现粗糙壁边界层的新物理，并为计算城市环境中大气污染物扩散的精度/效率设定新的标准。除了研究生，这个项目还将支持加州大学伯克利分校一名博士后研究员一年的时间。职业咨询和补助金撰写培训将通过与这两个私人投资机构的互动提供。学生班级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和自适应网格优化的当前页面。维基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了解。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). 0933642/0932613Chow/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.