Computational Framework for Multi-Scale Environmental Modelling

多尺度环境建模的计算框架

• 批准号: NE/H002847/1
• 负责人: Matthew Piggott
• 金额: $ 24.34万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH002847%2F1
• 关键词: Computational; Framework; Multi; Scale; Environmental

Convection is one of the most challenging problems in atmospheric science today. It covers highly energetic processes, like volcanic eruptions or biomass burning plumes, as well as fields of cumulus clouds or single deep thunderclouds. Standard atmospheric models, such as those used in weather forecasting or climate prediction, are generally not able to resolve the scales involved in convective activity. While cloud or plume sizes may well reach the 1km scale in the horizontal and 10km scale in the vertical, key processes, such as turbulent mixing that lead to extremely important entrainment (mixing environmental properties into the convective column) are of the scale of a few to tens of metres. Such convective processes are often responsible for fast vertical transport of pollutants from the boundary layer to higher atmospheric layers (in volcanic eruptions, or very deep convective clouds, up to the stratosphere), and therefore their correct simulation is highly crucial. Similarly, less vigorously convective but highly turbulent flows in complex topographies (urban or mountainous environments) are important for the dispersion of hazardous chemical species or for the development of wild fires. Such situations are challenging for the current generation of environmental numerical models. The overall purpose of this project is to couple and optimise two existing computational models (Imperial-FLUIDITY and Cambridge-ATHAM). ATHAM is a high-resolution atmospheric model with physical parameterisations for a wide range of plume and cloud relevant applications. ATHAM has successfully simulated atmospheric processes with high spatial resolution within a limited area for problems where topography and the interaction with the flow outside the computational domain are of secondary importance. FLUIDITY contains state-of-the-art parallel adaptive mesh methods that are able to optimally resolve flows, whilst being able to represent key force balances (geostrophic and hydrostatic) exactly which is important for accuracy and stability, and has been developed in its oceanographic guise of ICOM. FLUIDITY lacks the physical parameterisations for atmospheric problems that ATHAM will supply; however, it provides a general framework for CFD problems for a wide range of computational domains and resolutions. ATHAM-FLUIDITY will combine the best elements from both models. That is, the flexible adaptive mesh and balance maintaining finite element methods of FLUIDITY and the advanced physical models of ATHAM, allowing a new range of problems associated with global atmospheric models to be investigated. An important example is convection, which often develops within frontal systems that are part of the large-scale flow with topography and differential heating due to surface inhomogeneities often providing the perturbation that can trigger convection. The combined model will be able to capture large-scale flows as well as fine-scale features in areas of interest allowing a more efficient interaction of scales in one single model. Over the last decade, the programming paradigm has changed from structured to modular and object-oriented programming, in which any set of modern languages may be widely used. Therefore, combining a number of open-source codes and libraries with the physics and advanced numerical technologies contained within FLUIDITY and ATHAM offers an excellent opportunity to develop the combined ATHAM-FLUIDITY model as a next-generation environmental flow model. The main advantages of the resulting open-source model will be: (a) flexibility of the problem formulation; (b) multi-physics modelling to optimally represent the physics using parallel mesh adaptivity and; (c) modular design of the advanced component technologies (e.g. CAD-geometry and mesh generation, linear and non-linear solvers etc). ATHAM-FLUIDITY will be linked produce computational results that are more realistic and accurate than the existing software codes.

对流是当今大气科学中最具挑战性的问题之一。它涵盖了高能量的过程，如火山爆发或生物质燃烧羽流，以及积云或单个深雷雨云的区域。标准的大气模型，例如用于天气预报或气候预测的模型，通常无法解析对流活动所涉及的尺度。虽然云或羽流的大小在水平方向上可能达到1公里尺度，在垂直方向上可能达到10公里尺度，但导致极其重要的卷吸（将环境特性混入对流柱）的湍流混合等关键过程的尺度是几米至几十米。这种对流过程往往是污染物从边界层向更高大气层（火山爆发或非常深的对流云，直到平流层）快速垂直传输的原因，因此，正确的模拟非常关键。同样，在复杂地形（城市或山区环境）中，对流不太剧烈但湍流很大，这对危险化学品的扩散或野火的发展很重要。这种情况对目前这一代的环境数值模式具有挑战性。该项目的总体目的是耦合和优化两个现有的计算模型（帝国-FLUIDITY和剑桥-ATHAM）。ATHAM是一个高分辨率的大气模式，具有物理参数化，可用于各种与羽流和云有关的应用。ATHAM成功地模拟了有限区域内的高空间分辨率大气过程，解决了地形和与计算域外气流相互作用的问题。FLUIDITY包含最先进的并行自适应网格方法，能够最佳地解决流动问题，同时能够准确地表示关键的力平衡（地转和流体静力），这对准确性和稳定性非常重要，并且已经在其海洋学伪装中开发。FLUIDITY缺乏ATHAM将提供的大气问题的物理参数化;然而，它为广泛的计算域和分辨率的CFD问题提供了一个通用框架。ATHAM-FLUIDITY将联合收割机结合两种型号的最佳元素。也就是说，灵活的自适应网格和保持平衡的FLUIDITY有限元方法和先进的物理模型ATHAM，允许一系列新的问题与全球大气模型进行调查。一个重要的例子是对流，它经常在锋面系统内发展，锋面系统是大尺度流动的一部分，由于表面不均匀性，地形和差异加热经常提供可以触发对流的扰动。合并后的模型将能够捕捉大规模的流动以及在感兴趣的领域，允许在一个单一的模型更有效的规模互动的精细尺度的功能。在过去的十年中，编程范式已经从结构化转变为模块化和面向对象的编程，其中任何现代语言都可以广泛使用。因此，将大量开源代码和库与FLUIDITY和ATHAM中包含的物理和先进数值技术相结合，为开发ATHAM-FLUIDITY组合模型作为下一代环境流模型提供了绝佳的机会。由此产生的开放源码模型的主要优点是：（a）问题表述的灵活性;（B）多物理场建模，利用并行网格自适应性最佳地表示物理场;（c）先进组件技术的模块化设计（例如CAD几何和网格生成、线性和非线性求解器等）。ATHAM-FLUIDITY将被链接产生比现有软件代码更真实和准确的计算结果。

项目成果

Compressible Flows on Adaptive and Unstrucured Meshes with FLUIDITY

具有流动性的自适应和非结构化网格上的可压缩流

• DOI: 10.1063/1.3651984
• 发表时间: 2011
• 作者: Nelson R