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

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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.