Computational Methods for Multiscale Turbulent Reacting Flows

拟议研究的目标是在湍流反应流的多尺度模拟框架内开发计算方法。该框架是基于粗粒度和细粒度的混合框架(分别为.)模拟基于大涡模拟(LES)和随机低维模型，一维湍流(ODT)模型。ODT模型旨在捕捉湍流和分子传输以及化学/热释放之间的耦合。该框架由燃烧PI开发，用于直接模拟与湍流-化学相互作用相关的亚网格尺度物理；但是，它很容易在涉及三维确定解和低维随机解的多尺度驱动流动中得到更广泛的应用。本文提出的工作扩展了模型公式，以解决多尺度计算工具的发展，以耦合两种解决方案。这些方法包括基于物理的大涡模拟和ODT亚格子尺度应力匹配，以及基于小波变换的多分辨率实现方法。将制定和实施数据同化战略，以管理从随机解到高阶确定性大涡模拟解的统计数据转移。最后，将研究加速化学动力学和分子输运相结合的策略，以提高混合LES-ODT公式的计算效率。各种公式将通过直接数值模拟(DNS)进行验证。所提出的努力提出了一个新的模拟框架来研究燃烧流动。化石燃料和新型燃料的燃烧在美国和国外的能源消耗中占据了很大份额；随着计算资源和技术的不断扩大，燃烧流动模拟能力最终可以取代建造昂贵的发动机原型，加快从设计到生产的过程，并有助于减少污染物和温室气体的产生。燃烧模拟是复杂的，因为需要考虑从分子尺度到设备尺度的复杂物理；研究人员和他的同事将开发多尺度策略，通过混合模拟来模拟燃烧流动，这些模拟旨在解决不同尺度范围的物理问题。综合的结果是这些模拟的自举过程，导致在计算上有效的策略来表示燃烧流动中的大范围的尺度。这项工作的大部分工作需要深入了解燃烧流动的物理学以及对能源和环境的影响；但是，这项工作的其他方面利用了信息技术的进步(包括获取超级计算资源、软件的进步)和计算数学。

The objective of the proposed research is to develop computational methods within a multiscale modeling framework for turbulent reacting flows. The framework is based on hybrid coarse-grained and fine-grained(resp.) simulations based on large-eddy simulations (LES) and a stochastic low-dimensional model, the one-dimensional turbulence (ODT) model. The ODT model is designed to capture the coupling between turbulent and molecular transport and chemistry/heat release. The framework has been developed by the PI for combustion to directly model subgrid scale physics associated with turbulence-chemistry interactions; but, it can easily have broader applications for multiscale driven flows involving 3D deterministic solutions with low-dimensional stochastic solutions. The work proposed here extends the model formulation to address the development of multiscale computational tools to couple the two solution schemes. The approaches involve physics-based matching of filtered subgrid scale stresses between LES and ODT as well as the implementation multiresolution methods based on the wavelet transform. Data assimilation strategies will be formulated and implemented for managing the transfer of statistics from the stochastic solution to the high-order deterministic LES solution. Finally, strategies to accelerate the integration of chemical kinetics and molecular transport will be investigated to improve the computational efficiency of the hybrid LES-ODT formulation. The various formulations will be validated with direct numerical simulations (DNS).The proposed effort addresses a novel simulation framework to study combustion flows. The combustion of fossil and novel fuels make up the lion?s share of energy consumption in the US and abroad; and the ability to simulate combustion flows, with expanding computational resources and know-how, can eventually replace building expensive prototypes of engines, and speed up the design-to-production process, and help mitigate the generation of pollutants and greenhouse gases. Combustion simulation is complex, because an account of complex physics from the molecular scale to the device scale is required; the investigator and his colleagues will develop multiscale strategies to simulate combustion flows through hybrid simulations that are designed to addresses physics at different ranges of scales. The combined outcome is a bootstrapping process for these simulations that results in computationally efficient strategies to represent the broad ranges of scales in combustion flows. Much of the effort requires insight to the physics of combustion flows and energy and environmental implications; but, other aspects of the effort draw upon advances in information technology (including access to supercomputing resources, advances in software) and computational mathematics.