TED-AJ03-293 HEAT TRANSFER OF A BACKWARD-FACING STEP FLOW IN A DUCT AND ITS CONTROL
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概要
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In order to grasp the basis of the three-dimensional flow and thermal systems including flow separation and reattachment, heat transfer experiment has been done on a duct flow with a backward-facing step, which is the simplest geometry to realize the flow separation and reattachment. The treatment rectangular duct has a relatively small aspect ratio and thus might have large sidewall effects on the flow and thermal fields. However, no reliable data exist for such an aspect ratio, while many data are available for the two-dimensional channels having large aspect ratios. Thus, at the first stage of this study, spatial distributions of local heat transfer coefficients on the bottom wall downstream of the backward-facing step in a duct having small aspect ratio were obtained by making use of a thermo sensitive liquid crystal sheet. As an experimental parameter, flow Reynolds number was changed in relatively wide range from 1000 to 10000. For the help to grasp the related flow structures, flow visualizations were also carried out. Then, at the second stage of this study, local heat transfer coefficients were also measured when an accessing flow was perturbed by actuations of the mini size flaps spanwisely arranged along the step edge. Firstly, for every Reynolds number case, obtained spatial distributions of local Nusselt number suggest high three dimensionality of the flow and thermal fields, and its magnitude becomes larger as Reynolds number increases. However, the maximum Nusselt number on the wall always appears near the sidewall region even if the flow Reynolds number is varied within the experimental[figure] ranges. On the other hand, the streamwise location of the maximum Nusselt number was found to move closer to the step as Reynolds number increases from 1000 to 2300,then again it moves to the downward from 2300 to 10000 while the spanwise location of it is almost unchanged near the sidewall. The primary flow recirculation causes heat transfer deterioration just behind the step. The lowest heat transfer is obtained near the sidewall by a pair of tornado like vertical vortex having axes in the flow normal direction. Furthermore, it was also found that flap actuations intensively affect the heat transfer on the bottom wall, that is, the flap actuations can effectively change the flow structure and recover the heat transfer deterioration just behind the step especially in the studied laminar flow case.[figure]
- 一般社団法人日本機械学会の論文
著者
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NAKAMURA Kazuya
Department of Neurosurgery, Shinshu University School of Medicine
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Senda Mamoru
Department Of Mechanical Engineering Doshisha University
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Senda Mamoru
Department Of Mechanical And Systems Engineering Doshisha University
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Inaoka Kyoji
Department Of Mechanical System Engineering Doshisha University
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Inaoka Kyoji
Department Of Mechanical And Systems Engineering Doshisha University
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Nakamura Kazuya
Department Of Mechanical And Systems Engineering Doshisha University
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