Investigation of the effects of turbulent flow on energy and mass transfer close to solid surfaces

湍流是工业和环境中最常见的流体流动类型，但它仍然是物理学中未解决的问题之一。它混合和分散能量或质量（如化学品或颗粒）的能力在日常应用中发挥着关键作用，如石油和天然气管道中的流动，工业反应堆，混合，加热或冷却，以及大气和海洋。该项目的目标是利用先进的计算技术来了解湍流中通常观察到的流动特征对能量和质量传输的影响。这项研究的结果可能会导致有效的能源管理，有效的设计工业设备的热量和质量传递发生，以及更好地预测和控制污染物的扩散。通过这一项目产生的数据库将提供给科学界，通过这一项目产生的模拟数据将用于制作可用于K-12科学演示的湍流扩散动画。分子色散对湍流输运的影响，相干速度结构对输运性质的影响。这里的主要假设是，在预测标量传输的动量传递失败的原因是，只有一些速度结构参与湍流传输靠近壁，和范围内的尺度，参与转移取决于分子的色散效应。要回答的主要问题是甚大尺度运动（称为VLSM）在湍流输运中的作用，以及分子扩散和对流之间的相互作用如何影响各向异性湍流中颗粒的混合或分离。所提出的方法是使用拉格朗日方法进行分析的计算，该方法提供了对跨越几个数量级的普朗特数的流体范围的研究（例如，液态金属、气体、制冷剂和电化学流体），使得可以处理常规方法通常不适用于当前超级计算机的情况。预期的结果可能会导致一个综合模型的发展，用于预测和控制的湍流transport.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

Turbulence is the most common type of fluid flow in both the industry and the environment, while it is still one of the unsolved problems in physics. Its ability to mix and disperse energy or mass (like chemicals or particles) plays a key role in every day applications, like flows in oil and gas pipelines, in industrial reactors, in mixing, in heating or cooling, as well as in the atmosphere and in oceans. The goal of this project is to understand the effects of flow features that are commonly observed in turbulent flow on the transport of energy and mass using advanced computational techniques. The findings of this research could lead to efficient energy management, efficient design of industrial equipment where heat and mass transfer take place, and better prediction and control of pollutant dispersion. The database generated through this project will become available to the scientific community, and simulation data generated through this project will be used to develop animations of turbulent dispersion that can be used in K-12 science demonstrations.Central concerns for the development of a comprehensive turbulent transport theory have been the prediction of the spatial variation of turbulent viscosity, the effect of molecular dispersion on turbulent transport, and the effect of coherent velocity structures on the transport properties. The main hypothesis here is that the reason for the failure in predicting scalar transfer from momentum transfer is that only some of the velocity structures participate in turbulent transfer close to a wall, and the range of scales that participate in the transfer depends on molecular dispersion effects. Main questions to be answered are what is the role the very large scales of motion (known as VLSM) in turbulent transport, and how the interplay between molecular diffusion and convection affects mixing or separation of particles in anisotropic turbulence. The proposed approach is to use computations with Lagrangian methods for analysis, which afford the study of a range of fluids that span several orders of Prandtl number in magnitude (e.g., liquid metals, gases, refrigerants, and electrochemical fluids) making it possible to handle cases where conventional methods are often not feasible with the current supercomputers. Expected results could lead to the development of a comprehensive model for the prediction and control of turbulent transport.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.