@article{fdi:010097038,
  title = {{F}ormation of dilute versus concentrated pyroclastic density currents in the impact zone of eruptive fountains : an experimental study},
  author = {{P}enlou, {B}. and {R}oche, {O}livier and van den {W}ildenberg, {S}. and {V}alentine, {G}. {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e study the physical mechanisms that operate in impact zones of collapsing fountains during explosive volcanic eruptions. {T}o this end, we simulate the formation of pyroclastic density currents in analogue laboratory experiments by releasing a mixture of glass particles of different sizes from a hopper, which impact the base of a horizontal channel. {A}coustic attenuation measurements and high-speed imaging are used to monitor the particle concentration and velocity of falling mixtures just before impact. {O}ver the course of the experiments, we identify two successive distinct regimes primarily governed by the particle concentration of the falling mixtures, which decreases over time. {T}he first is an early decoupled regime, where particles settle in the impact zone to form a concentrated granular flow overlain by a dilute particle cloud. {T}he second is a late coupled regime, in which particles remain entrained with the carrier air, resulting in a dilute suspension. {A}t the transition between the regimes, we find a power-law relationship between particle concentration and the {S}tokes number, suggesting that these two parameters play an important role in controlling impact zone processes. {W}e compare our results to recent numerical simulations on pyroclastic fountains and discuss relevant parameters that control the impact dynamics of pyroclastic mixtures.},
  keywords = {{P}yroclastic fountains ; {P}yroclastic current ; {P}yroclastic flow ; {E}xperiment},
  booktitle = {},
  journal = {{B}ulletin of {V}olcanology},
  volume = {88},
  numero = {5},
  pages = {55 [16 p.]},
  ISSN = {0258-8900},
  year = {2026},
  DOI = {10.1007/s00445-026-01971-z},
  URL = {https://www.documentation.ird.fr/hor/fdi:010097038},
}