1997 Volume 40 Issue 4 Pages 550-557
The characteristics of low-speed streaks in the turbulent channel flow of a drag-reducing surfactant solution are studied by employing the hydrogen-bubble flow visualization method. The mean velocity profiles and the distributions of streamwise turbulence intensity are also obtained. It is shown that, at a large drag reduction rate DR, the profile of the streamwise turbulence intensity has a plateau region around its peak. In the drag-reducing flow, the mean spanwise streak spacing reaches minimum at some distance from the wall. In the drag-reducing flow of high-density(1000 ppm)surfactant solution, the low-speed streaks appear intermittently at the Reynolds number smaller than those for the 'hump' of the f-Re curve(f:friction factor). The mean spanwise streak spacing very near the wall increases as DR becomes large. It is speculated that the nondimensional wall-normal distance y+ of the center of streamwise vortices is larger for the flow of large DR compared with that for the Newtonian fluid flow.
JSME international journal. Ser. 1, Solid mechanics, strength of materials
JSME international journal. Ser. A, Mechanics and material engineering
JSME international journal. Ser. 3, Vibration, control engineering, engineering for industry
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JSME International Journal Series A Solid Mechanics and Material Engineering