NDLI: Effects of 3-D Local Unsteadiness on Heat Transfer Prediction in Turbulated Passages

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Pamela, A. Mcdowell William, D. York Walters, D. Keith James, H. Leylek
Copyright Year	2003
Abstract	A newly developed unsteady turbulence model was used to predict heat transfer in a turbulated passage typical of turbine airfoil cooling applications. Comparison of fullyconverged computational solutions to experimental measurements reveal that accurate prediction of heat transfer coefficient requires the effects of local small-scale unsteadiness to be captured. Validation was accomplished through comparison of the time- and area-averaged Nusselt number on the passage wall between adjacent ribs with experimental data from the open literature. The straight channel had a square cross-sectional area with multiple rows of staggered and rounded-edge ribs on opposite walls that were orthogonal to the flow. Simulations were run for Reynolds numbers of 5500, 16500, and 25000. Computational solutions were obtained on a multi-block, multi-topology, unstructured, and adaptive grid, using a pressure-correction based, fully-implicit Navier-Stokes solver. The computational results include two-dimensional (2-D) and three-dimensional (3-D) steady and unsteady simulations with viscous sublayers resolved (y+ ≤ 1) on all the walls in every case. Turbulence closure was obtained using a new turbulence model developed in-house for the unsteady simulations, and a realizable k-ε turbulence model was used for the steady simulations. The results obtained from the unsteady simulations show greatly improved agreement with the experimental data, especially at realistically high Reynolds numbers. The key 3-D physics mechanisms responsible for the successful outcome include: (1) shear layer roll-up over the turbulators; (2) recirculation zones both upstream and downstream of the rib faces; and (3) reattachment regions between each rib pair. Results from the unsteady case are superior to those of the steady because they capture the aforementioned mechanisms, and therefore more accurately predict the heat transfer.
Sponsorship	Heat Transfer Division
Starting Page	107
Ending Page	118
Page Count	12
File Format	PDF
ISBN	0791837181
DOI	10.1115/IMECE2003-42268
Volume Number	Heat Transfer, Volume 2
Conference Proceedings	ASME 2003 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2003-11-15
Publisher Place	Washington, DC, USA
Access Restriction	Subscribed
Subject Keyword	Cfd Rans Unsteady Turbulence modeling Turbulated passage Heat transfer Turbulence
Content Type	Text
Resource Type	Article

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