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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

ROUGH CHANNELS

pages 11-20
DOI: 10.1615/TSFP6.20
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要約

Flows past rough surfaces are different from those past smooth walls and have been, in the past, studied experimentally because of their importance in several practical applications. Three regimes were observed, laminar, fully turbulent and transitional. The first one does not present any difference with that for smooth walls. In the second one has been observed experimentally that the resistance does not depend on the Reynolds number. A confirmation of this behaviour by DNS is not presently available, however the DNS has been used to understand the physics of rough flows. In particular it has been shown that the normal to the wall velocity fluctuations (u2) play a fundamental role. In the present study the transitional regime, where the resistance depends on Re and on the shape of the obstacles, has been studied by DNS, and has been confirmed that also in this regime u2 at the plane of the crests is the critical quantity.

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