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Comparison of Turbulent Thermal Diffusivity and Scalar Variance ModelsIn this study, several variable turbulent Prandtl number formulations are examined for boundary layers, pipe flow, and axisymmetric jets. The model formulations include simple algebraic relations between the thermal diffusivity and turbulent viscosity as well as more complex models that solve transport equations for the thermal variance and its dissipation rate. Results are compared with available data for wall heat transfer and profile measurements of mean temperature, the root-mean-square (RMS) fluctuating temperature, turbulent heat flux and turbulent Prandtl number. For wall-bounded problems, the algebraic models are found to best predict the rise in turbulent Prandtl number near the wall as well as the log-layer temperature profile, while the thermal variance models provide a good representation of the RMS temperature fluctuations. In jet flows, the algebraic models provide no benefit over a constant turbulent Prandtl number approach. Application of the thermal variance models finds that some significantly overpredict the temperature variance in the plume and most underpredict the thermal growth rate of the jet. The models yield very similar fluctuating temperature intensities in jets from straight pipes and smooth contraction nozzles, in contrast to data that indicate the latter should have noticeably higher values. For the particular low subsonic heated jet cases examined, changes in the turbulent Prandtl number had no effect on the centerline velocity decay.
Document ID
20160010069
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Yoder, Dennis A.
(NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
August 5, 2016
Publication Date
January 4, 2016
Subject Category
Aeronautics (General)
Report/Patent Number
GRC-E-DAA-TN28421
Meeting Information
Meeting: AIAA SciTech Conference
Location: San Diego, CA
Country: United States
Start Date: January 4, 2016
End Date: January 8, 2016
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
WBS: WBS 794072.02.03.02.01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
computational fluid dynamics
turbulence models
turbulent heat transfer
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