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| Titel |
Turbulent and viscous sediment transport – a numerical study |
| VerfasserIn |
O. Durán, B. Andreotti, P. Claudin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: Sediment Transport and Landscape Dynamics (SALADYN) Workshop 2012 ; Nr. 37 (2014-05-06), S.73-80 |
| Datensatznummer |
250121291
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| Publikation (Nr.) |
 copernicus.org/adgeo-37-73-2014.pdf |
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| Zusammenfassung |
| Sediment transport is studied as a function of the grain to fluid density
ratio using two phase numerical simulations based on a discrete element
method (DEM) for particles coupled to a continuum Reynolds averaged
description of hydrodynamics. At a density ratio close to unity (typically
under water), sediment transport occurs in a thin layer at the surface of the
static bed, and is called bed load. Steady, or "saturated" transport is
reached when the fluid borne shear stress at the interface between the mobile
grains and the static grains is reduced to its threshold value. The number of
grains transported per unit surface therefore scales as the excess shear
stress. However, the fluid velocity in the transport layer remains almost
undisturbed so that the mean grain velocity scales with the shear velocity
u*. At large density ratio (typically in air), the vertical velocities are
large enough to make the transport layer wide and dilute. Sediment transport
is then called saltation. In this case, particles are able to eject others
when they collide with the granular bed. The number of grains transported per
unit surface is selected by the balance between erosion and deposition and
saturation is reached when one grain is statistically replaced by exactly one
grain after a collision, which has the consequence that the mean grain
velocity remains independent of u*. The influence of the density ratio is
systematically studied to reveal the transition between these two transport
regimes. Finally, for the subaqueous case, the grain Reynolds number is
lowered to investigate the change from turbulent and viscous transport. |
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