HR: 14:40h
AN: V23E-05    [Abstracts]
TI: High Mobility of Erosive Granular Flows and Surge Generation
AU: * Mangeney, A
EM: mangeney@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, Universite Paris 7, 4 Place Jussieu, Paris, 75005, France
AU: * Mangeney, A
EM: mangeney@ipgp.jussieu.fr
AF: Institut for NonLinear Science, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0402, United States
AU: Tsimring, L
EM: ltsimring@ucsd.edu
AF: Institut for NonLinear Science, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0402, United States
AU: Volfson, D
EM: dvolfson@ipgp.jussieu.fr
AF: Institut for NonLinear Science, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0402, United States
AU: Aronson, I
EM: aronson@msd.anl.gov
AF: Argonne National Laboratory, 9700 South Cass Avenue, Argone, IL 60439, United States
AU: Bouchut, F
EM: bouchut@ens.fr
AF: Departement de Mathematiques et Applications, ENS, 45 rue d'Ulm, Paris, 75005, France
AB: Dense granular flows driven by gravity, such as avalanches or some pyroclastic flows, are active processes that participate in the evolution of the surface of the Earth and other telluric planets. They also represent natural hazards that are a threat to many populations and infrastructures. However, natural granular flows are still poorly understood. In particular, the origin of the high mobility of pyroclastic flows or the occurrence of surges during the propagation of gravitational flows along the slope are challenging questions. Fundamentally different mechanisms were employed to explain the high mobility of these flows. Among these processes, the erosion of material already present on the underlying solid topography is expected to play a significant role in the mobility of debris or pyroclastic flows and overall dynamics of transportation. When static granular material is entrained into motion by the flowing material, no-flow and flowing zones not only coexist but exchange mass and momentum. The effect of entrainment on granular flows dynamics is a key issue in volcanology where natural flows often propagate on slopes covered by the deposits of former events. The static/flowing transition is taken explicitly into account in the new theory proposed by Aranson and Tsimring [2002]. A model based on this approach is used here to simulate the spreading of granular material over an erodible bed. Numerical results show that the presence of even a very thin layer of granular material lying on the solid bed strongly increases the mobility of granular flows. Furthermore, as the thickness of the granular layer increases, the dynamics of the flowing mass drastically changes from a decelerating flow to a steadily travelling wave. Although natural gravitational flows are more complex, these results show that erosion processes could significantly increase the mobility of pyroclastic flows and make it possible to generate surges.
DE: 0545 Modeling (4255)
DE: 0560 Numerical solutions (4255)
DE: 0742 Avalanches
DE: 1810 Debris flow and landslides
DE: 1815 Erosion
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting