There is a substantial need to better understand multi-physics interactions in realistic laboratory experiments, yet it is currently unfeasible to perform direct numerical simulations (DNS) of most such problems. As a result, reduced-order models such as those used to represent unclosed subgrid-scale stresses in large-eddy simulations (LES) and advanced numerical techniques, including adaptive mesh refinement and nested grid structures, are required for the study of multi-physics interactions in practical situations. In particular, it is now possible to model many real-world flows with LES fidelity, and to selectively refine the computational mesh in a small region of the domain to resolve multi-physics interactions with DNS fidelity. However, rules and guidance for the valid implementation of this multi-fidelity ‘hybrid LES-DNS’ approach have yet to be fully formulated. Within the embedded DNS region, multi-physics interactions will be influenced by (i) macroscale features (e.g. large-scale shear gradients or body forces that produce turbulence), (ii) LES-regulated mesoscale features (e.g. advecting turbulent eddies), and (iii) microscale features that are subgrid-scale to the LES (e.g. layers of fast-reacting intermediate chemical species). In this study, we address the second of these effects, which poses particular challenges due to the transfer and overlapping nature of advecting mesoscale eddies between the purely LES (i.e. macroscale) and purely DNS (i.e. microscale) regions. By combining dimensional analysis and computational results, we formulate a scaling law for the required depth of the transition zone surrounding the embedded DNS region within hybrid LES-DNS computations of realistic turbulent flows.

中文翻译：

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混合 LES-DNS 中所需过渡区深度的标度律

在现实的实验室实验中，迫切需要更好地理解多物理场相互作用，但目前对大多数此类问题进行直接数值模拟 (DNS) 是不可行的。因此，多物理场研究需要降阶模型，例如用于表示大涡模拟 (LES) 中未闭合亚网格尺度应力的模型和高级数值技术，包括自适应网格细化和嵌套网格结构。实际情况中的互动。特别是，现在可以使用 LES 保真度对许多现实世界的流进行建模，并有选择地细化域的小区域中的计算网格，以解决具有 DNS 保真度的多物理场交互。然而，有效实施这种多保真“混合 LES-DNS”方法的规则和指南尚未完全制定。在嵌入的 DNS 区域内，多物理场相互作用将受到 (i) 宏观特征（例如产生湍流的大规模剪切梯度或体力），（ii）LES 调节的中尺度特征（例如对流湍流涡流）和(iii) LES 亚网格尺度的微尺度特征（例如快速反应的中间化学物质层）。在这项研究中，我们解决了其中的第二个影响，由于在纯 LES（即宏观尺度）和纯 DNS（即微观尺度）区域之间平流中尺度涡流的转移和重叠性质，它带来了特殊的挑战。通过结合量纲分析和计算结果，