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| Titel |
New developments in the analysis of column-collapse pyroclastic density currents through numerical simulations of multiphase flows |
| VerfasserIn |
S. Lepore, C. Scarpati |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 1 ; Nr. 3, no. 1 (2012-06-08), S.161-173 |
| Datensatznummer |
250000844
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| Publikation (Nr.) |
 copernicus.org/se-3-161-2012.pdf |
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| Zusammenfassung |
| A granular multiphase model has been used to evaluate the action of
differently sized particles on the dynamics of fountains and associated
pyroclastic density currents. The model takes into account the overall
disequilibrium conditions between a gas phase and several solid phases, each
characterized by its own physical properties. The dynamics of the granular
flows (fountains and pyroclastic density currents) has been simulated by
adopting a Reynolds-averaged Navier-Stokes model for describing the
turbulence effects. Numerical simulations have been carried out by using
different values for the eruptive column temperature at the vent, solid
particle frictional concentration, turbulent kinetic energy, and
dissipation. The results obtained provide evidence of the multiphase nature of
the model and describe several disequilibrium effects. The low concentration
(≤5 × 10−4) zones lie in the upper part of the granular
flow, above the fountain, and above the tail and body of pyroclastic density
current as thermal plumes. The high concentration zones, on the contrary,
lie in the fountain and at the base of the current. Hence, pyroclastic
density currents are assimilated to granular flows constituted by a low
concentration suspension flowing above a high concentration basal layer
(boundary layer), from the proximal regions to the distal ones. Interactions
among the solid particles in the boundary layer of the granular flow are
controlled by collisions between particles, whereas the dispersal of
particles in the suspension is determined by the dragging of the gas phase.
The simulations describe well the dynamics of a tractive boundary layer
leading to the formation of stratified facies during Strombolian to Plinian
eruptions. |
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