Publications des scientifiques de l'IRD

Roche Olivier, Gilbertson M.A., Phillips J.C., Sparks R.S.J. (2004). Experimental study of gas-fluidized granular flows with implications for pyroclastic flow emplacement. Journal of Geophysical Research Solid Earth, 109 (B10), B10201 [p. NIL_20-NIL_33]. ISSN 0148-0227.

Titre du document
Experimental study of gas-fluidized granular flows with implications for pyroclastic flow emplacement
Année de publication
2004
Type de document
Article référencé dans le Web of Science WOS:000227038500002
Auteurs
Roche Olivier, Gilbertson M.A., Phillips J.C., Sparks R.S.J.
Source
Journal of Geophysical Research Solid Earth, 2004, 109 (B10), B10201 [p. NIL_20-NIL_33] ISSN 0148-0227
Experiments have been carried out on initially gas-aerated and gas-fluidized granular flows propagating into a horizontal channel. After lateral acceleration following release of the originally fluidized bed, two contrasting flow behaviors were observed, which reflected the degree of initial fluidization and the grain size. Initial fluidization disrupts the interparticle contact network, which controls internal friction of the static bed. The flow regime then depends on the timescale needed to reestablish a strong contact network, and this time increases as the grain size decreases. Initially aerated and fluidized flows of coarse particles (>approximate to100 mum) and initially aerated flows of fine particles (<&AP; 100 μm) behave as their nonfluidized counterparts and they propagate as a wedge, with decelerating velocities so that the front position increases as the &SIM;0.8 power of time. In contrast, initially fluidized flows of fine particles propagate for most of their duration at constant thickness and frontal velocity in a similar fashion to the slumping regime of buoyancy-driven gravity currents of Newtonian fluids. We have determined a Froude number Fr for such flows of &AP;2.6 consistent with published data from experimental and theoretical investigations on inviscid fluids. This implies that internal particle friction can be neglected in describing the dynamics of initially fluidized, concentrated fine granular flows. However, all flows are characterized by a short, final stopping phase whose timescale gives an estimate of the kinetics required to reestablish a strong contact network and form a static deposit. These results suggest that fines-rich pyroclastic flows may propagate as inviscid fluids for most of their emplacement.
Plan de classement
Géologie et formations superficielles [064]
Localisation
Fonds IRD [F B010046764]
Identifiant IRD
fdi:010046764
Contact