Intellectual Merit: The overall goal of the proposed research is to explore the fundamental mechanism of turbulent heat transfer in the case of anisotropic turbulence. The specific objectives for the duration of the project are to: (a) investigate the physical mechanisms for turbulent transport close to a solid boundary (in the viscous wall region and in the logarithmic layer); (b) determine the Prandtl number effects on turbulent transport properties (e.g., on the turbulent Prandtl number and on the Nusselt number); (c) develop algorithms for the simulation of coupled heat and fluid flow and for chemically reacting turbulent flows. The proposed approach is to use hydrodynamics generated by direct numerical simulations to generate Lagrangian data for turbulent dispersion. This Lagrangian approach allows to investigate fluids of practical interest but different properties (e.g., liquid metals, gases, refrigerants, electrochemical fluids), and to investigate cases where conventional numerical methods are often not feasible with the current capabilities of supercomputers. Broader Impact of the Proposed Activities: The findings of this research will be significant for the theory of turbulent transport as well as for industrial and environmental applications, in which modeling turbulent transport is important (e.g., design of chemical reactors, design of heat exchangers for different Prandtl number fluids, prediction and control of pollutant dispersion, heat transfer over moving blades). Aspects of the proposed research project will be instrumental in the development of a continuing education course. In addition, the database generated through this project will become available to the community through a web server that our group is already operating. Finally, an effort will be initiated to organize workshops focused on the identification of modeling issues in turbulent transport and of databases that can serve as validation benchmarks.
The goals of this project were to investigate the mechanism with which heat or species molecules are transported inside a turbulent flow, such as inside a chemical reactor, or around a sea vessel or an aircraft, or even in the event of the release of toxic chemicals in the atmosphere due to a terrorist attack or an accident. Even though we literary live in a turbulent world, where flow of water in rivers and oceans, and the movement of air in the atmosphere is turbulent, questions about the origin of turbulence and the actual mechanics of how exactly turbulence disperses heat and mass have not been fully answered. The more we understand about these questions, the better we can predict natural phenomena and the better we can control industrial and environmental processes. Specifically in this project, the interplay between the complicated turbulent flow and the movement of molecules was examined with newly discovered, sophisticated computational techniques. Detailed simulations of the flow were conducted and the trajectories of thousands of individual particles moving within the flow and because of it were monitored in space and time, providing a clear view of transport. The simulations even provided information backwards in time, as we tried to determine from where the molecules that are observed at a location in the flow are coming from. The results obtained and published to the scientific community can be used to develop new simulation models for improving the design of several pieces of industrial equipment, where heat and mass are mixed in complicated flows, in addition to furthering scientific understanding for the way that turbulence works. Finally, the computational techniques developed as part of this project are now being used in different applications, to shed light into the transport of species and fine particles in porous materials (like subsurface rocks for oil and gas exploration and production), expanding the impact of this research project to other areas of science.
