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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
https://doi.org/10.5194/gmd-2018-224
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Model description paper 17 Oct 2018

Model description paper | 17 Oct 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).

IMEX_SfloW2D 1.0. A depth-averaged numerical flow model for pyroclastic avalanches

Mattia de' Michieli Vitturi1, Tomaso Esposti Ongaro1, Giacomo Lari2, and Alvaro Aravena3 Mattia de' Michieli Vitturi et al.
  • 1Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Via della Faggiola 32, 56126 Pisa, Italy
  • 2Università degli Studi di Pisa, Dipartimento di Matematica, Largo Pontecorvo 1, 56126 Pisa, Italy
  • 3Università degli Studi di Firenze, Dipartimento di Scienze della Terra, Via La Pira, 50121 Firenze, Italy

Abstract. Pyroclastic avalanches are a type of granular flow generated at active volcanoes by different mechanisms, including the collapse of steep pyroclastic deposits (e.g., scoria and ash cones) and fountaining during moderately explosive eruptions. They represent end-members of gravity-driven pyroclastic flows, characterized by relatively small volumes (less than about 1Mm3) and relatively thin (1–10m) layers at high particle concentration (1–50vol.%), manifesting strong topographic control. The simulation of their dynamics and mapping of their hazards pose several different problems to researchers and practitioners, mostly due to the complex and still poorly understood rheology of the polydisperse granular mixture, and to the interaction with the complex natural three-dimensional topography, which often causes rapid rheological changes. In this paper, we present IMEX_SfloW2D, a depth-averaged flow model describing the granular mixture as a single-phase granular fluid. The model is formulated in absolute Cartesian coordinates (where the fluid flow equations are integrated along the direction of gravity) and can be solved over a topography described by a Digital Elevation Model. The numerical discretization and solution algorithms are formulated to allow a robust description of wet-dry conditions (thus allowing to accurately track the front propagation) and to implicitly solve the non-linear friction terms. Owing to these features, the model is able to reproduce steady solutions, such as the triggering and stopping phases of the flow, without the need of empirical conditions. Benchmark cases are discussed to verify the numerical code implementation and to demonstrate the main features of the new model. A preliminary application to the simulation of the February 11th pyroclastic avalanche at Etna volcano (Italy) is finally presented. In the present formulation, a simple semi-empirical friction model (Voellmy-Salm rheology) is implemented. However, the modular structure of the code facilitates the implementation of more specific and calibrated rheological models for pyroclastic avalanches.

Mattia de' Michieli Vitturi et al.
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Short summary
Pyroclastic avalanches are a type of granular flow generated at active volcanoes by different mechanisms, including the collapse of steep pyroclastic deposits (e.g., scoria and ash cones) and fountaining during moderately explosive eruptions. We present IMEX_SfloW2D, a depth-averaged flow model describing the granular mixture as a single-phase granular fluid. Benchmark cases and preliminary application to the simulation of the February 11th pyroclastic avalanche at Mt. Etna (Italy) are shown.
Pyroclastic avalanches are a type of granular flow generated at active volcanoes by different...
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