Expansion ratio effects on three-dimensional separated flow and heat transfer around backward-facing steps

被引:23
作者
Kitoh, Aya
Sugawara, Kazuaki
Yoshikawa, Hiroyuki [1 ]
Ota, Terukazu
机构
[1] Tohoku Univ, Dept Aerosp Engn, Sendai, Miyagi, Japan
[2] Kumamoto Univ, Dept Mech & Syst Engn, Kumamoto 8608555, Japan
[3] Tohoku Univ, Dept Mech Syst & Design, Sendai, Miyagi, Japan
来源
JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME | 2007年 / 129卷 / 09期
关键词
separated and reattached flow; forced convection; heat transfer; backward-facing step; DNS;
D O I
10.1115/1.2739619
中图分类号
O414.1 [热力学];
学科分类号
摘要
Direct numerical simulation methodology clarified the three-dimensional separated flow and heat transfer around three backward-facing steps in a rectangular channel, especially effects of channel expansion ratio ER upon them. ER treated in the present study was 1.5, 2.0, and 3.0 under a step aspect ratio of 36.0. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The present numerical results for ER = 2.0 were found to be in very good agreement with the previous experimental and numerical ones in the present Reynolds number range for both the steady and unsteady flow states. The time averaged reattachment length on the center line increases with a decrease of ER. The flow became unsteady at RE=700, 600, and 500 for ER=1.5, 2.0, and 3.0, respectively, accompanying the remarkable increase of the three-dimensionality of the flow and temperature fields in spite of a very large step aspect ratio of 36.0. The Nusselt number increases in the reattachment flow region, in the neighborhood of the sidewalls, and also in the far downstream depending on both Re and ER.
引用
收藏
页码:1141 / 1155
页数:15
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