Roche Olivier auteur aut IRD Phillips J.C. auteur aut IRD Kelfoun Karim auteur aut IRD text bookSection eng text/pdf born digital access This chapter summarizes the principal experimental and theoretical approaches used to investigate the physics of pyroclastic density currents (PDCs), which are gravity driven hot gas–particle mixtures commonly generated during explosive volcanic eruptions. PDC behavior ranges from pyroclastic surges, which are dilute turbulent suspensions, to pyroclastic flows, which are dense (fluidized) granular avalanches. Most PDCs consist of a coupled basal flow and an overriding surge, which renders their physics particularly complex. Experiments and phenomenological theory have been used to characterize the propagation and deposition mechanisms of PDCs. Most work has used turbulent gravity currents as an analogue to dilute PDCs and has provided fundamental insight into propagation and deposition dynamics and mixing with their surroundings. Dense PDCs have been investigated as granular and fluidized flows, and these studies have provided insight into deposit levée-channel morphology typical of coarse-grained flows, shown that fines-rich flows may behave as inertial fluid currents, and suggested that deposits of PDCs may form by aggradation. Numerical formulations ranging from continuum depth-averaged to discrete element models have been used to simulate PDC emplacement on real topographies and are fundamental in the context of volcanic hazard assessment and mitigation. specialized VOLCANISME ROCHE VOLCANIQUE PYROCLASTITE PROPRIETE PHYSIQUE PROPAGATION DYNAMIQUE MODELE MATHEMATIQUE ERUPTION VOLCANIQUE 066GPHGEN 020MATH01 Fagents S.A. ed. edt IRD Gregg T.K.P. ed. edt IRD Lopes R.M.C. ed. edt IRD 203-229 Cambridge Cambridge University Press 2013 https://www.documentation.ird.fr/hor/fdi:010060249 10.1017/CBO9781139021562.010 978-0-521-89543-9 [F B010060249] https://www.documentation.ird.fr/hor/fdi:010060249 https://www.documentation.ird.fr/intranet/publi/depot/2020-10-27/010060249.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2013-12-20 2020-11-12 fdi:010060249 fre