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| Titel |
Multi-scale coupling strategy for fully two-dimensional and depth-averaged models for granular flows |
| VerfasserIn |
Shiva P. Pudasaini, Birte Domnik, Stephen A. Miller |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078458
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| Zusammenfassung |
| We developed a full two-dimensional Coulomb-viscoplastic model and applied it for inclined
channel flows of granular materials from initiation to their deposition. The model includes the
basic features and observed phenomena in dense granular flows like the exhibition of a yield
strength and a non-zero slip velocity. A pressure-dependent yield strength is proposed to
account for the frictional nature of granular materials. The yield strength can be
related to the internal friction angle of the material and plays an important role, for
example, in deposition processes. The interaction of the flow with the solid boundary is
modelled by a pressure and rate-dependent Coulomb-viscoplastic sliding law. We
developed an innovative multi-scale strategy to couple the full two-dimensional, non
depth-averaged model (N-DAM) with a one-dimensional, depth-averaged model
(DAM). The coupled model reduces computational complexity dramatically by using
DAM only in regions with smooth changes of flow variables. The numerics uses
N-DAM in regions where depth-averaging becomes inaccurate, for instance, in the
initiation and deposition regions, and (particularly) when the flow hits an obstacle or a
defense structure. In these regions, momentum transfer must be, and is, considered
in all directions. We observe very high coupling performance, and show that the
numerical results deviate only slightly from results of the much more cumbersome full
two-dimensional model. This shows that the coupled model, which retains all the basic
physics of the flow, is an attractive alternative to an expensive, full two-dimensional
simulations.
We compare simulation results with different experimental data for shock waves appearing
in rapid granular flows down inclined channels and impacting a wall. The model
predicts the evolution of the strong shock wave and the impact force on a rigid
wall for different inclination angles and sliding surfaces. It is demonstrated that
the internal friction angle plays an important role in the deposition process, and
show that classical depth-averaged models cannot accurately describe the flow
dynamics of material impinging on a rigid wall. Therefore, depth-averaged models
should not be used as stand-alone models, but can be used successfully as part of a
multi-scale coupling strategy. This novel and computationally economic strategy has
great potentiality to be used in the large scale natural snow avalanches and debris
flows.
References:
Domnik, B., and S. P. Pudasaini (2012): Full two-dimensional rapid chute flows of simple
viscoplastic granular materials with a pressure-dependent dynamic slip-velocity and their
numerical simulations. J. Non-Newtonian Fluid Mech., 173-174, 72-86.
Pudasaini, S. P., K. Hutter, S.-S. Hsiau, S.-C. Tai, Y. Wang, and R. Katzenbach (2007): Rapid
flow of dry granular materials down inclined chutes impinging on rigid walls. Phys. Fluids,
19(5), 053302, doi:10.1063/1.2726885. |
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