ISSN:
1573-1987
Keywords:
drag reduction
;
riblets
;
sediment transport
;
turbulence
;
coherent structures
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract A turbulent flow at modest Reynolds numbers (26,000–32,000, as defined in the text) over flat erodible sandy beds was investigated. The beds were composed of sand grains of uniform size with a diameter smaller than the viscous sublayer of the flow. When a modest sand transport (1.2 × 10-3–8.5 × 10-3 g/s·cm) was present, the near-wall coherent structures of the flow produced a bed form with a streaky longitudinal pattern. This pattern had a lateral spacing of about 100 viscous units and had less drag than a flat wall. The mechanism causing the drag reduction is due to a low-frequency riblet pattern which allows the flow to sustain higher wall shear stresses without additional erosion. That means during the riblet regime the sediment transport remains quasi-constant. The formation of the sand streaks as well as the drag reducing mechanism are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1009990129943
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