Use of Direct Numerical Simulations and Lagrangian Methods in Turbulent Transport

由于需要比实验室研究中获得的更详细的温度和速度场统计信息，湍流传热分析的进展受到限制。提出的研究通过使用超级计算机计算随时间变化的三维温度和速度场来响应这一需求。它在三个方面是新颖的：它在很大范围的普朗特数上提供结果。第一次将欧拉和拉格朗日的结果联系起来。它探讨了使用拉格朗日方法来描述沉积物的搬运。通常处理输运问题的方法是使用欧拉框架，用微分方程来描述空间中固定体积内的浓度变化。本研究中需要探索的一个观点是，通过使用拉格朗日框架，物理理解以一种更自然的方式出现，拉格朗日框架将运输物种（热标记物或沉积物）的浓度场视为由许多源和汇的贡献产生的。对于所考虑的问题，基本组成部分是边界处的极小源和极小源的色散。头部传输系统是紊流通过通道，其中底壁被加热，顶壁被冷却。对Pr=0.05-40进行直接数值模拟。拉格朗日方法将用于将这些扩展到高达2000的普朗特数。将考虑水平矩形河道中泥沙的湍流输运。

ABSTRACT CTS-9503000 Thomas Hanratty Univ. of Illinois Advances in the analysis of turbulent heat transfer have been limited because of the need for more detailed information about the statistics of the fluctuating temperature and velocity fields than is obtained in laboratory studies. The proposed research responds to this need by using supercomputers to calculate the time-dependent, three-dimensional temperature and velocity fields. It is novel in three ways: It supplies results over a wide range of Prandtl numbers. I relates (for the first time) Eulerian and Lagrangian results. It explores the use of Lagrangian methods to describe sediment transport. The usual approach to transport problems is to use an Eulerian framework in which a differential equation is written to describe the concentration changes in a fixed volume in space. A viewpoint to be explored in this research is that physical understanding emerges in a more natural way by using a Lagrangian frame work, which considers concentration fields of a transported species (thermal markers or sediment) as resulting from the contributions of a number of sources and sinks. For the problems considered, the fundamental building block is dispersion from and infinitesimal source at the boundary. The head transfer system is turbulent flow through a channel in which the bottom wall is heated and the top wall is cooled. Direct numerical sumulations will be carried out for Pr=0.05-40. Lagrangian methods will be used to extend these to Prandtl numbers as high as 2000. Turbulent transport of sediment in a horizontal rectangular channel will be considered.