Assessment of motion-induced fluidization of dense pyroclastic gravity currents

P. Salatino

Abstract


The paper addresses some fundamental aspects of the dynamics of dense granular flows down inclines relevant
to pyroclastic density currents. A simple mechanistic framework is presented to analyze the dynamics of the
frontal zone, with a focus on the establishment of conditions that promote air entrainment at the head of the current
and motion-induced self-fluidization of the flow. The one-dimensional momentum balance on the current
along the incline is considered under the hypothesis of strongly turbulent flow and pseudo-homogeneous behaviour
of the two-phase gas-solid flow. Departures from one-dimensional flow in the frontal region are also analyzed
and provide the key to the assessment of air cross-flow and fluidization of the solids in the head of the current.
The conditions for the establishment of steady motion of pyroclastic flows down an incline, in either the
fluidized or «dry» granular states, are examined.

Keywords


pyroclastic flow;fluidization;gravity current

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References


DOI: https://doi.org/10.4401/ag-3238
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X