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| Titel |
Experimental investigation of the influence of the sediment size distribution on bedload transport |
| VerfasserIn |
M. Houssais, E. Lajeunesse |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063682
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| Zusammenfassung |
| We report the results of an experimental investigation of bedload transport of a bimodal
sediment bed. The experiments are carried out in a tilted rectangular flume, partially filled
with an erodible bed composed of a mixture of 2 populations of quartz grains of sizes
D1 = 0.7mm and D2 = 2.2mm, respectively. The sediment bed is sheared by a steady and
spatially uniform turbulent flow. Using a high-speed video imaging system, we measure the
average velocity and the surface density of the moving particles of each size fraction. We
show that they follow laws similar to those reported by Lajeunesse et al. [2010a] for an
homogenous sediment bed. Indeed, noting Ïi* and Ïc,i*, the Shields and threshold Shields
number calculated for the grain size Di, we find that (1) the surface density of
moving particles increases linearly with Ïi*- Ïc,i*; (2) the average particle velocity
increases linearly with Ïi*1-2 - Ïc,i*1-2, with a finite nonzero value at threshold. The
influence of the sediment bed size distribution appears to be encoded in the value of
the threshold Shields number which is found to vary with the proportion of small
grains. |
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