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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

VORTEX-JET MECHANISM IN A CHANNEL WITH SPHERICAL DIMPLES FOR HEAT TRANSFER AUGMENTATION

pages 321-326
DOI: 10.1615/TSFP6.510
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RÉSUMÉ

Vortex mechanism of heat transfer enhancement in a narrow channel with dimples has been investigated numerically using LES method. The flow separation results in a formation of vortex structures which significantly enhance heat transfer on dimpled surfaces conducted by a small increase of the pressure loss. The heat transfer To get a deep insight into flow physics LES is performed for single phase flow in a channel with a spherical dimple. The instantaneous vortex formation and separation are investigated inside the dimple area. Considered are Reynolds numbers (based on dimple print diameter) ReD = 20000 and ReD = 40000 and the depth to print diameter ratio of Δ = 0.26. Frequency analysis of LES data revealed the presence of two dominating frequencies in unsteady flow oscillations. Direct analysis of the flow field revealed the presence of coherent vortex structure inclined to the mean flow. The structure changes its orientation in time causing the long period oscillations with opposite-of-phase motion. Three dimensional proper orthogonal decomposition (POD) analysis is carried out on LES pressure and velocity fields to identify spatio-temporal structures hidden in the random fluctuations. Tornado-like spatial POD structures have been determined inside dimples.

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