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| Titel |
Influence of obstacles on the dynamics of rapid granular chute flows |
| VerfasserIn |
C. Kroner, S. P. Pudasaini, S. A. Miller |
| 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 |
250060968
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| Zusammenfassung |
| We experimentally and numerically analyze the influence of obstacles on the dynamics of a
rapid granular chute flow. A high-speed camera is used to capture the detailed flow processes
and to extract the flow velocities, flow geometry and the interface between the solid- and
fluid-type granular regimes through the flow depth. First, a short inclined plane that fits with
the channel width is introduced with a relative angle of 45° to the down-slope direction. PVC
and sand, with only a small difference in internal friction angles, are analyzed in
detail. PVC (with smaller friction angle, Ï = 33°) overflows the obstacle without
depositing the material while flowing. Steady-state flow is quickly established for
this material. However, as the sand (with a slightly larger internal friction angle,
Ï = 37°) encounters the obstacle, it begins to settle, and consequently shock waves
develop until a steady state is reached where the flow occurs only in a relatively thin
fluidized surface layer over the deposited material. This demonstrates that a small
difference in the internal friction angle can lead to fundamental changes in the
flow-obstacle interactions in rapid granular flows down slopes. This is a significant
advance in our understanding. The second obstacle (which also covers the channel
width) is a long wall erected perpendicular to the channel. We analyzed in detail
the influence of the inflow velocity and height, and the inclination angle of the
channel, on the deposition processes that includes strong shock wave generation and
propagation.
We compare our experimental results with a new two-dimensional numerical channel
flow simulation. A parametric analysis is performed for varying angles and lengths
of the obstacle, the internal and bottom friction angles, inclination angles of the
chute, and the inflow velocities and heights. In the vicinity of the flow obstacle
interaction, large gradients in the flow fields (e.g., velocity and pressure) can develop
in the direction of the flow depth. Because we can determine in detail the basic
parameters and the dynamical quantities of the flow in these flow configurations, our
physical model and numerical simulation method significantly improves on the
typical depth averaged models. Our findings improve the understanding of rapid
granular flows around obstacles, and thus helps in design and construction of more
effective catching dams and for improved prediction of overtopping of existing
dams. |
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