US-UK Cooperative Research: Structure of Turbulence Near Density Interfaces

该奖项将支持亚利桑那州立大学的Harindra Fernando博士和英国剑桥大学应用数学和理论物理系J.C.R.Hunt博士在机械工程方面的合作研究。这项研究的目的是研究密度界面附近的湍流结构。这项研究将主要是理论/数字性质的(将在剑桥大学进行)，但也建议进行补充实验室实验(将在亚利桑那州立大学进行)。发展对与密度界面上的湍流混合有关的物理过程的清楚理解以及对这种现象的模拟仍然是流体力学中具有挑战性的问题。这项拟议的研究将基于一项新技术，即所谓的“湍流运动学模拟”，该技术是由亨特博士在剑桥的团队开发的。这种特殊的方法与以前的方法的不同之处在于，显式地考虑了通过随机移动不同大小和频率的“大”涡而在界面上平流的“小”湍流旋涡的影响。界面上的内波产生与这种平流直接相关。该分析将对几种具有地球物理和工程意义的流动形态进行分析，其中包括速度剪切和零均值剪切湍流作用下的密度界面。理论预测将与实验室测量结果进行比较。这项研究的结果将大大有助于理解密度界面上的湍流混合。该项目将受益于两位研究人员在均质、分层和旋转流动中的湍流问题上的广泛和互补的专业知识。

This award will support collaborative research in mechanical engineering between Dr. Harindra Fernando, Arizona State University and Dr. J.C.R. Hunt, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, England. The objective of the proposed research is an investigation of the structure of turbulence near density interfaces. The research will be mainly of a theoretical/numerical nature (to be carried out at the University of Cambridge), but complementary laboratory experiments (to be performed at Arizona State University) are also proposed. The development of a clear understanding of the physical processes associated with turbulent mixing across density interfaces and the modelling of such phenomena continue to be challenging problems in fluid mechanics. The proposed research will be based on a new technique, the so-called "kinematic simulation of turbulence", which has been developed by Dr. Hunt's group at Cambridge. This particular approach differs from earlier ones in the sense that the effects of "small" turbulent eddies, advected over the interface by randomly moving "large" eddies of different sizes and frequencies, are explicitly considered. The internal-wave generation at the interface is directly related to this advection. The analysis will be performed for several flow configurations of geophysical and engineering interest, that include density interfaces subjected to velocity shear and zero-mean-shear turbulence. The theoretical predictions will be compared with the laboratory measurements. The results of this study will contribute substantially to the understanding of turbulent mixing across density interfaces. The project will benefit from the extensive and complementary expertise of the two investigators on the topic of turbulence in homogenous, stratified and rotating flows.