境界層遷移に及ぼす円柱後流の影響 : 第2報,すき間比の流れ場に与える影響

概要

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An experimental investigation was conducted to determine the mechanism and conditions of governing the boundary-layer transition phenomena which were induced by a circular cylinder placed at some distance apart from a plate. The cylinder of 1.0 mm in diameter was placed 0.25 m downstream from the leading edge of the plate, and gap to diameter ratios were selected to be 0.3, 0.5 and 0.6. These ratios were chosen because they were found to have different characteristics on the boundary-layer transition in the former experiments. Mean velocity distribution, intensity of turbulence and distribution spectra in the wake flow were measured for each gap condition under the unit Reynolds number of U_0/ν=3.5×10^5 (m<-1>). The results obtained are as follows. In the case of the gap ratio of 0.6, boundary-layer transition occurs by the direct interference between the wake of the cylinder and the laminar boundary-layer of the plate. On the contrary, the transition at the ratio of 0.5 is observed to be shed from the cylinder. In the case of the ratio of 0.3, no vortices were observed and the mechanism of transition was similar to that of a tripping wire which has no gap with the plate.
社団法人日本機械学会の論文
1988-11-25