円柱冷却によって低レイノルズ数で発生する冷却渦列 : 第2報,冷却後流の渦度構造と冷却渦列の発生メカニズム(熱工学,内燃機関,動力など)

概要

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A circular cylinder wake of air with negative buoyancy at low Reynolds numbers was analyzed numerically, and a vorticity structure in the cooled wake and a generation mechanism of the cooled vortex street were made clear as follows: With increasing the cooling rate, the angle between shear layers increased and the wake width became large. Furthermore the wake vorticity was generated and the vorticity quantity of shear layers increased. As a result, the shear layers were elongated, and the region with the vorticity near the tips of shear layers became large. These tips rolled up and reached the midplane in the wake mutually. Thus the stable wake, i. e. the cooled vortex street, was formed. The stable rolling of shear layer tips was realized in only the Karman and the cooled vortex streets. Thermo-fluid behavior is extremely different among three groups, i. e. (i) the isothermal wake, Karman vortex street, and oscillating twin-vortex, (ii) the transient flow, and cooled vortex street, and (iii) the symmetric flow. When a flow changes to a different group flow, the coefficient of shear stress and mean Nusselt number on cylinder stuface decreases abruptly.
一般社団法人日本機械学会の論文
2004-05-25