@article{fdi:010087478,
  title = {{E}xperimental measurement of enhanced and hindered particle settling in turbulent gas-particle suspensions, and geophysical implications},
  author = {{P}enlou, {B}. and {R}oche, {O}livier and {M}anga, {M}. and van den {W}ildenberg, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he dynamics of geophysical dilute turbulent gas-particles mixtures depends to a large extent on particle concentration, which in turn depends predominantly on the particle settling velocity. {W}e experimentally investigate air-particle mixtures contained in a vertical pipe in which the velocity of an ascending air flux matches the settling velocity of glass particles. {T}o obtain local particle concentrations in these mixtures, we use acoustic probing and air pressure measurements and show that these independent techniques yield similar results for a range of particle sizes and particle concentrations. {M}oreover, we find that in suspensions of small particles (78 mu m) the settling velocity increases with the local particle concentration due to the formation of particle clusters. {T}hese clusters settle with a velocity that is four times faster than the terminal settling velocity of single particles, and they double settling speeds of the suspensions. {I}n contrast, in suspensions of larger particles (467 mu m) the settling velocity decreases with increasing particle concentration. {A}lthough particle clusters are still present in this case, the settling velocity is decreased by 30%, which is captured by a hindered settling model. {T}hese results suggest an interplay between hindered settling and cluster-induced enhanced settling, which in our experiments occur respectively at {S}tokes number {O}(100) and {O}(1). {W}e discuss implications for volcanic plumes and pyroclastic currents. {O}ur study suggests that clustering and related enhanced or hindered particle settling velocities should be considered in models of volcanic phenomena and that drag law corrections are needed for reliable predictions and hazard assessment.},
  keywords = {gas-particle suspension ; particle settling ; clustering ; explosive volcanism ; turbulent flow ; acoustic probing ; {CHILI} ; {LLAIMA}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {S}olid {E}arth},
  volume = {128},
  numero = {3},
  pages = {e2022{JB}025809 [16 p.]},
  ISSN = {2169-9313},
  year = {2023},
  DOI = {10.1029/2022jb025809},
  URL = {https://www.documentation.ird.fr/hor/fdi:010087478},
}