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| Titel |
PLUME-MoM 1.0: A new integral model of volcanic plumes based on the method of moments |
| VerfasserIn |
M. de' Michieli Vitturi, A. Neri, S. Barsotti |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-06), S.2447-2463 |
| Datensatznummer |
250116502
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| Publikation (Nr.) |
 copernicus.org/gmd-8-2447-2015.pdf |
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| Zusammenfassung |
| In this paper a new integral mathematical model for volcanic plumes, named
PLUME-MoM, is presented. The model describes the steady-state dynamics of a
plume in a 3-D coordinate system, accounting for continuous variability in
particle size distribution of the pyroclastic mixture ejected at the vent.
Volcanic plumes are composed of pyroclastic particles of many different sizes
ranging from a few microns up to several centimeters and more. A proper
description of such a multi-particle nature is crucial when quantifying
changes in grain-size distribution along the plume and, therefore, for better
characterization of source conditions of ash dispersal models. The new model
is based on the method of moments, which allows for a description of the
pyroclastic mixture dynamics not only in the spatial domain but also in the
space of parameters of the continuous size distribution of the particles.
This is achieved by formulation of fundamental transport equations for the
multi-particle mixture with respect to the different moments of the grain-size
distribution. Different formulations, in terms of the distribution of the
particle number, as well as of the mass distribution expressed in terms of
the Krumbein log scale, are also derived. Comparison between the new
moments-based formulation and the classical approach, based on the
discretization of the mixture in N discrete phases, shows that the new model
allows for the same results to be obtained with a significantly lower
computational cost (particularly when a large number of discrete phases is
adopted). Application of the new model, coupled with uncertainty
quantification and global sensitivity analyses, enables the investigation of the
response of four key output variables (mean and standard deviation of the
grain-size distribution at the top of the plume, plume height and amount of
mass lost by the plume during the ascent) to changes in the main input
parameters (mean and standard deviation) characterizing the pyroclastic
mixture at the base of the plume. Results show that, for the range of
parameters investigated and without considering interparticle processes such
as aggregation or comminution, the grain-size distribution at the top of
the plume is remarkably similar to that at the base and that the plume height
is only weakly affected by the parameters of the grain distribution. The
adopted approach can be potentially extended to the consideration of key
particle–particle effects occurring in the plume including particle
aggregation and fragmentation. |
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