Use of Direct Numerical Simulations and Lagrangian Methods in Turbulent Transport

摘要CTS-9503000托马斯汉拉蒂大学。由于需要比实验室研究更详细的关于脉动温度和速度场统计的信息，在湍流换热分析方面的进展一直受到限制。这项拟议的研究通过使用超级计算机来计算与时间相关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：它提供了广泛范围的普朗特数字的结果。我(第一次)叙述了欧拉和拉格朗日的结果。它探索了使用拉格朗日方法来描述泥沙运移。解决运输问题的通常方法是使用欧拉框架，在该框架中写出一个微分方程式来描述空间中固定体积内的浓度变化。这项研究中要探索的一个观点是，物理认识通过使用拉格朗日框架以更自然的方式出现，该框架将运输的物种(热标记或沉积物)的浓度场视为多个源和汇的贡献的结果。对于所考虑的问题，基本的积木是边界上的色散和无穷小源。头部传输系统是通过通道的湍流流动，在该通道中底壁被加热，顶壁被冷却。对于Pr=0.05-40，将进行直接数值计算。拉格朗日方法将被用来将这些扩展到高达2000的普朗特数。将考虑水平矩形渠道中泥沙的湍动输运。

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.