| Budget Amount *help |
¥4,940,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥1,140,000)
Fiscal Year 2018: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000)
Fiscal Year 2017: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000)
Fiscal Year 2016: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
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| Outline of Final Research Achievements |
The mechanism of pressure drag generation was investigated for a channel flow with transverse roughness elements on one wall. The square rod roughness elements is arranged with the roughness pitch ratio of 2, 4 and 8. The friction coefficient increases with the roughness pitch ratio. The increment is due to the pressure drag acting on the roughness. The pressure drag is occurred by the transport of Reynolds shear stress above the cavity between roughness elements. The profiles of the second invariant of the mean velocity gradient tensor have a negative value near the downstream side wall in the cavity, and the absolute value increases with the roughness pitch ratio. The negative value of the invariant contributes to positive pressure on the side wall and the value of the positive pressure depends on the roughness pitch ratio.
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