PyroCLAST: a new experimental framework to investigate overspilling of channelized, concentrated pyroclastic currents - Archive ouverte HAL Access content directly
Journal Articles Bulletin of Volcanology Year : 2022

PyroCLAST: a new experimental framework to investigate overspilling of channelized, concentrated pyroclastic currents

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Abstract

Small-volume concentrated pyroclastic currents (CPCs) are often responsible for unpredicted and deadly overspills from channel confines when they encounter an abrupt change in propagation direction. We present the first results obtained with a new experimental facility, PyroCLAST, built to investigate the mechanisms of such overspills. The apparatus consists of a 5-m-long flume with a 45° valley bend at mid-distance from the source, and whose slope angle varies from 3 to 15°. Glass beads of 45–90-μm diameter are initially fluidized in a reservoir and rapidly released into the flume through a vertical sliding gate. Experiments are recorded using video cameras to measure the temporal evolution of both the parent channelized and overbank flow velocity and discharge rate, using particle image velocimetry. Overspills are generated when the flows interact with the bend, at slope angles of 9 to 15°, generating a front splash and an overbank flow. Results demonstrate that the slope angle favors the formation of overspill by increasing the flow discharge rate, causing a local increase of the flow thickness along the bend (i.e., superelevation) that overtops the channel sidewall. Moreover, under constant initial conditions, a high channel slope angle and discharge rate favor the development of discrete, internal flow pulses, and a positive correlation is found between the runout of the channelized flows and that of overbank deposits. Data collected in this study will also constitute a reference dataset for future benchmarking of CPC numerical models.
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hal-03924443 , version 1 (09-01-2023)

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V. Gueugneau, S. Charbonnier, Olivier Roche. PyroCLAST: a new experimental framework to investigate overspilling of channelized, concentrated pyroclastic currents. Bulletin of Volcanology, 2022, 85 (1), pp.5. ⟨10.1007/s00445-022-01623-y⟩. ⟨hal-03924443⟩
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