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、被动标量的湍流输运是一种常见的现象，它在发动机工业、电厂、建筑环境以及大气边界层空气污染预报等方面有着重要的应用。从本质上讲，由切应力、压力梯度和标量梯度驱动的湍流对流是非定常的，表现出与标量输运过程高度相互作用的相干流动结构。 这项研究的目的是利用大涡模拟(LES)的方法，更深入地了解光滑和粗糙壁面边界层中流动结构的动态演变和标量输送过程之间的相互作用，并发展新的基于物理的亚格子尺度标量通量模型，用于改进低雷诺数和高雷诺数湍流标量输送的亚网格尺度通量模型。为了实现这些目标，将使用先验和后验大涡模拟方法来检验模型在光滑壁边界层流动和绕障碍阵列的湍流边界层流动中的性能。所获得的大涡模拟结果将用直接数值模拟数据和两组综合水槽和风洞实验数据进行验证。 预计拟议的研究将为申请者及其团队提供一个极好的机会，就开发一种高保真预测工具进行创新研究，该工具可供学者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送。还预计拟议的研究将提供一个机会，培训与计算流体动力学、湍流热质传递、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有关的高素质人员。

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.