@article{fdi:010064634,
  title = {{T}owards a quantitative understanding of pyroclastic flows : effects of expansion on the dynamics of laboratory fluidized granular flows},
  author = {{G}irolami, {L}. and {D}ruitt, {T}. {H}. and {R}oche, {O}livier},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e conducted laboratory dam-break experiments on initially fluidized granular flows using two different fine-grained powders (mean grain sizes 47 and 67 mu m) down a smooth, horizontal channel with an impermeable base. {T}he powders were first fluidized and expanded to a known degree in the flume reservoir, then released down the channel by opening a sliding gate. {T}he mixture formed rapidly moving flows that defluidized and deposited progressively as they propagated. {T}he experiments were similar to those carried out previously using volcanic ash by {G}irolami et al. (2008, 2010) but explored a much larger range of initial aspect ratios (height-to-length ratio, a = 0.25 to 4). {T}hey were designed to investigate the effects of initial expansion (up to 50 vol.% above loose packing) and aspect ratio on the dynamics of flow propagation and deposition, and to explore different scalings in order to determine the physical parameters governing these processes. {T}he flows exhibit a similar behaviour to other types of transient granular flows, including three well defined propagation phases (acceleration, constant velocity, and stopping phases) and the progressive aggradation of a basal static layer during emplacement. {T}he deposit aggradation velocity depends only on the initial powder expansion and is similar to that of a collapsing bed of the same powder, expanded by the same amount, under quasi-static, non-shearing conditions. {A}t a given initial expansion, the maximum runout distance scales with the initial bed height h(0), the runout duration with (h(0)/g)(1/2) and the maximum velocity with (gh(0))(1/2). {H}owever, runout distance and duration both increase with increasing initial expansion. {T}his is attributed to the effect of hindered settling in delaying defluidization of the dense, but slightly expanded, suspension. {T}he data enable us to identify an additive scaling law providing a smooth transition from non-expanded to expanded flows.},
  keywords = {{P}yroclastic flows ; {F}luidized granular flows ; {L}aboratory experiments ; {S}caling laws ; {P}hysical processes},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {296},
  numero = {},
  pages = {31--39},
  ISSN = {0377-0273},
  year = {2015},
  DOI = {10.1016/j.jvolgeores.2015.03.008},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064634},
}