| Budget Amount *help |
¥4,940,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥1,140,000)
Fiscal Year 2017: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2016: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2015: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
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| Outline of Final Research Achievements |
Direct numerical simulations and laboratory experiments of a turbulent channel flow with an innovative three-dimensional riblet were performed, of which the lateral spacing of the adjacent walls is sinusoidally varied in the streamwise direction. A largest drag-reduction rate of about 12% is obtained by means of parametric studies. The present riblet respectively induces a downward and upward flows in the expanded and contracted regions, resulting in the decrease of the Reynolds shear stress. Vortical structures in the vicinity of the riblets were advected along the induced flow, and the vortices were deteriorated. As a result, the region of the high wall shear stress in the enlarged part of the riblet is localized. Consequently, a high drag reduction effect can be obtained.
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