日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
円柱に働く抗力の軽減と伝熱促進 : 小さなロッドによる流れ場の制御
筒井 敬之五十嵐 保
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62 巻 (1996) 597 号 p. 1802-1809

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A small rod was set upstream of a circular cylinder for enhancement of heat transfer and reduction of drag of the circular cylinder. The diameter of the cylinder was 40mm, and that of the rod d was varied from 1 to 12 mm. The distance between the axes of the cylinder and rod L was varied from 50 to 120mm, and Reynolds number ranged from 1.5×104 to 6.2×104. The local heat transfer distribution has a maximum at the angle of ±30∼35°from the front stagnation point, regardless of the presence or absence of vortex shedding from the rod. Therefore, the heat transfer at the front face increases markedly. Beyond Re≥3.1×104, a second maximum of heat transfer appears at φ=±11O°upon transition to turbulent flow. In the separated region at the rear face, the heat transfer decreases. The overall heat transfer increases with an increase in d/D and a decrease in L/D. This method is useful for higher Reynolds numbers. The optimum conditions are d/D=0.25 and L/D=1.25, that is, the case in which quasi-stationary vortices are formed between the rod and the cylinder. In this case, the overall heat transfer increases by 40%, and the total drag coefficient included the drag of the rod is reduced by 43% compared to that of without the rod.

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