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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

DES AND URANS DOWNSTREAM OF A HEATED BACKWARD-FACING STEP: A COMPARATIVE STUDY

DOI: 10.1615/TFESC1.cmd.013160
pages 353-363

Sebastian Ruck
Karlsruhe Institute of Technology, Institute of Neutron Physics and Reactor Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Frederik Arbeiter
Karlsruhe Institute of Technology, Institute of Neutron Physics and Reactor Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany


KEY WORDS: Detached Eddy Simulation, URANS, heated backward facing step, heat transfer, flow reattachment, asymmetrical heated cooling channel flows

Abstract

Heat transfer and fluid characteristics downstream of a heated backward-facing step were predicted by Detached-Eddy-Simulations and Unsteady-Reynolds-Averaged-Navier-Stokes-Simulations at a Reynolds number of Re=2.8E4 (based on the step height and at a Reynolds number of Re=1.12E5 based on the hydraulic diameter of a corresponding channel respectively). A constant heat flux density was applied along the lower wall leading to a heat up rate of q+=6.8E-5. The channel size was 4h × 4h × 33h and the channel expansion ratio was 1.25. DES and URANS were performed with the k-ω-SST and k-ε-realizable eddy-viscosity models. Mean temperature, heat transfer quantities and turbulent heat fluxes were compared with approved and published benchmark data. The flow and heat transfer physics are dominated by the unsteady turbulent flow structures of the separated and reattached free shear layer. The corresponding quantities differ for both numerical approaches and the turbulence models. DES results are in good agreement with benchmark data. It is shown that DES is a method for an accurate prediction of local heat transfer and corresponding flow characteristics of turbulent flows including separation and reattachment. Hence, it is suggested for the thermal design of heat transfer devices at Reynolds numbers in the range of Re=1E5 to Re=1E6, i.e. high pressure helium running asymmetrically heated, rib-roughened cooling channels.

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