E121 低速ストリークの不安定特性に対するストリーク形状の影響

概要

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In order to examine the nature of streak instability experimentally, a single low-speed streak is produced by a small piece of screen set normal to the wall in a laminar boundary layer. The lateral width and height of the screen are varied systematically to see the dependency of the streak instability on the geometry of the streak. The results show that when the lateral width of the low-speed streak is greater than three or four times the shear-layer thickness, the streak instability to symmetric varicose modes are not so different from that of the two-dimensional Kelvin-Helmholtz instability of the velocity profile in the normal-to-wall direction. The growth rate of symmetric mode is rapidly decreased with decreasing the streak width, and the Kelvin-Helmholtz instability is completely suppressed when the lateral width approaches the shear layer thickness. On the other hand, the instability to anti-symmetric sinuous disturbances, which is essentially governed by the wake profiles across the streak, is not sensitive to the streak width, but is decreased with decreasing the vertical scale of the low-speed streak.
日本流体力学会の論文
2001-07-31