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Main Title: The dynamics of volcanic jets
Subtitle: Temporal evolution of particles exit velocity from shock‐tube experiments
Author(s): Cigala, V.
Kueppers, U.
Peña Fernández, J. J.
Taddeucci, J.
Sesterhenn, J.
Dingwell, D. B.
Type: Article
Language Code: en
Abstract: Pyroclast ejection during explosive volcanic eruptions occurs under highly dynamic conditions involving great variations in flux, particle sizes, and velocities. This variability must be a direct consequence of complex interactions between physical and chemical parameters inside the volcanic plumbing system. The boundary conditions of such phenomena cannot be fully characterized via field observation and indirect measurements alone. In order to understand better eruptive processes, we conducted scaled and controlled laboratory experiments. By performing shock‐tube experiments at known conditions, we defined the influence of physical boundary conditions on the dynamics of pyroclast ejection. If applied to nature, we are focusing in the near‐vent processes where, independently of fragmentation mechanism, impulsively released gas‐pyroclast mixtures can be observed. These conditions can be met during, e.g., Strombolian or Vulcanian eruptions, parts of Plinian eruptions, or phreatomagmatic explosions. The following parameters were varied: (1) tube length, (2) vent geometry, (3) particle load, (4) temperature, and (5) particle size distribution. Gas and particles in the experiments are not coupled (St >> 1). The initial overpressure, with respect to atmosphere, was always at 15 MPa. We found a positive correlation of pyroclast ejection velocity with (1) particle load, (2) diverging vent walls, and (3) temperature as well as a negative correlation with (1) tube length and (2) particle size. Additionally, we found that particle load strongly affects the temporal evolution of particle ejection velocity. These findings stress the importance of scaled and repeatable laboratory experiments for a better understanding of volcanic phenomena and therefore volcanic hazard assessment.
Issue Date: 24-Jul-2017
Date Available: 28-May-2018
DDC Class: 550 Geowissenschaften
Subject(s): volcanic jets
pyroclast velocity
explosive dynamics
Journal Title: Journal of geophysical research : JGR
Publisher: Wiley
Publisher Place: Hoboken, NJ
Volume: 122
Issue: 12
Publisher DOI: 10.1002/2017JB014149
Page Start: 6031
Page End: 6045
ISSN: 2169-9356
Appears in Collections:FG Numerische Fluiddynamik » Publications

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