Large-Eddy Simulation of Turbulent Scalar Transport Processes in Smooth and Rough Wall Boundary Layers

在机械、环境和化学工程中，边界层中主动和被动标量的湍流输运是经常遇到的现象，在发动机工业、电厂、建筑环境、大气边界层大气污染预测等方面都有重要的应用。从本质上讲，由剪应力、压力梯度和标量梯度驱动的湍流对流是不稳定的，并且表现出与标量输运过程高度相互作用的连贯流动结构。**本研究旨在利用大涡模拟（large-eddy simulation， LES）方法更深入地了解光滑和粗糙边界层中动态演变的流动结构与标量输运过程之间的相互作用，并开发新的基于物理的亚网格尺度标量通量模型，以改进低雷诺数和高雷诺数流动中湍流标量输运的LES。为了实现这些目标，将采用先验和后验的LES方法来测试模型在光滑壁面边界层流动和湍流边界层在障碍物阵列上流动的性能。将利用直接数值模拟（DNS）数据和两组综合水渠风洞实验数据对所得的LES结果进行验证。**预计拟议的研究将为申请人和他的团队提供一个极好的机会，进行高保真度预测工具的创新研究，该工具可以被学术界和工程师用于评估不同类型边界层流动中的主动和被动标量输运。此外，预计拟议的研究将为培养计算流体动力学、湍流传热传质、环境弥散和基于内部代码和超级计算机的高性能科学计算等领域的高素质人才提供机会

In mechanical, environmental and chemical engineering, turbulent transport of active and passive scalars in a boundary layer is a frequently encountered phenomenon, which has important applications for the engine industry, power plants, building environment, and prediction of air pollution in the atmospheric boundary layer. By their nature, turbulent convective flows driven by shear stresses, pressure gradients and scalar gradients are unsteady, and exhibit coherent flow structures that are highly interactive with the scalar transport processes. ** The proposed research aims at obtaining a deeper understanding of the interaction between dynamically evolving flow structures and scalar transport processes in both smooth and rough-wall boundary layers using the method of large-eddy simulation (LES), as well as development of new physics-based subgrid-scale scalar-flux models for improved LES of turbulent scalar transport in both low- and high-Reynolds number flows. In order to achieve these goals, both a priori and a posteriori LES methods will be employed for testing the model performance in contexts of smooth-wall boundary-layer flows and turbulent boundary-layer flows over obstacle arrays. The obtained LES results will be validated against direct numerical simulation (DNS) data and two sets of comprehensive water-channel and wind-tunnel experimental data.** It is anticipated that the proposed research will provide an excellent opportunity for the applicant and his team to conduct innovative research on development of a high-fidelity predictive tool that can be used by both academics and engineers for assessing active and passive scalar transport in different types of boundary-layer flows. It is also anticipated that the proposed research will provide an opportunity to train highly qualified personnel in areas related to computational fluid dynamics, turbulent heat and mass transfer, environmental dispersion, and high-performance scientific computing based on in-house codes and supercomputers.**