| Budget Amount *help |
¥5,460,000 (Direct Cost: ¥4,200,000、Indirect Cost: ¥1,260,000)
Fiscal Year 2014: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2013: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2012: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
|
|---|
| Outline of Final Research Achievements |
The drag-reduction effect of an innovative three-dimensional riblet is evaluated, and world's largest drag-reduction rate of 12% is obtained. Vortical structures in wall turbulence over the riblet surface are investigated by means of a dual-plane stereoscopic particle image velocimetry measurement. It is found that the drag-reduction mechanism is similar to those of two-dimensional riblets. A different point is that the present riblet respectively induces a downward and upward flows in the expanded and contracted regions, which prevent vortices from hitting the bottom wall with wider lateral spacing of the riblet. In consequence, the wetted area of the present riblet is smaller than those of two-dimensional riblets, resulting in the high drag-reduction effect.
|
