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Research Abstracts Online
January - December 2011

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University of Minnesota Twin Cities
College of Science and Engineering
Department of Mechanical Engineering

PI: Terrence W. Simon, Associate Fellow

Reynolds Averaged Navier-Stokes and Large Eddy Simulations of Turbulent Flow and Heat Transfer in Propulsion and Power Systems

This group performs research in Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) of turbulent and transitional flows of interest in aerodynamics, power, and propulsion systems. With RANS, equations are closed by low-Reynolds number turbulence models, whereas in LES, only the subgrid scales are modeled. LES has recently been employed to study the influence of heat transfer, rotation, and buoyancy on the structure of turbulence in configurations of interest in engineering applications. The main research activities are the simulations of flows in complex geometries using the immersed boundary treatment, and the simulation of particle-laden flows. The long-term objective of the research is twofold. The first is to evaluate the accuracy of LES, RANS, and subgrid turbulence models by comparing predicted results with experimentally measured ones. The second is to contribute to the physical understanding of flows and transition in aerodynamics and propulsion systems. Another portion of the present work is the simulation of flows in turbine passages in support of measurements of thermal migration of coolant and unsteady flow associated with transition, wake passings, and separation. In the high-pressure turbine, the migration of coolant used to protect passage surfaces is important in evaluation of thermal stresses on the endwall of the passage. Measurements are underway and simulations of this flow will be carried out in parallel. In the low-pressure turbine, unsteady flow separation, transition, and wake-influenced events proceed in a periodic fashion. The researchers are measuring velocity profiles in this flow and will carry out parallel computation work in support.

In a DARPA-funded project on electronics cooling, the group is using agitators and synthetic jets to disturb the flow to enhance the heat transfer performance of the cooling system allowing air cooling of next-generation electronic devices. The numerical simulation will support the design of the experiments and optimization within the parameter space. The agitators and synthetic jets are simulated separately using dynamic meshes in FLUENT. The combined system is also simulated. Computations of the dynamics and structure of the devices driven by piezoelectric materials using structures programs such as ANSYS are used to improve the design of the agitator and synthetic jet assemblies.

The group is also doing a project that will develop a localized compressed air approach for storing excess energy from off-shore wind turbines to dramatically smooth variations in power supply and demand imbalances during the day. A less efficient version of this concept is already in use today whereby excess electricity is used to compress air, and the stored energy is extracted by burning hydrocarbon fuel in a gas turbine. In this approach, the energy as available prior to conversion to electricity is stored and an efficient compressor/expander that operates nearly isothermally is used directly for energy storage and extraction. Simulations are done using commercial software packages like ANSYS and FLUENT to model the isothermal compression/expansion. Support will come from data collected experimentally, which include parametric studies in support of experiment design. Simulations are helpful in studying possible trends.

Group Members

Smita Agrawal, Graduate Student
Longzhong Huang, Graduate Student
Farhad A. Jaberi, Department of Mechanical Engineering, Michigan State University
Richard Pletcher, Department of Mechanical Engineering, Iowa State University
Zhaohui Qin, Department of Mechanical Engineering, Iowa State University
Andrew Rice, Graduate Student
Yuhyen Seah, Graduate Student
Congshun Wang, Research Associate
Wen Wang, Department of Mechanical Engineering, Iowa State University
Taiho Yeom, Graduate Student
Youmin Yu, Research Associate
Chao Zhang, Graduate Student
Min Zhang, Research Associate