Numerical investigation of reverse segregation in debris flows by DEM

Studies of the mechanisms and the effects on the flowing mobility for hazardous geophysical flows (e.g., debris flows) is crucial for hazard mitigation and prediction. Granular flows with grains of mixed sizes are numerically modeled and the contact behavior of solid particles is fundamentally studied using the discrete element method. The mechanical effects of particle contacts (shearing and collision) are contrasted with geometrical effects (kinetic sieving) to explain the mechanism of reverse segregation. Compared to granular flows with uniform solid particles, the effect of segregation on granular flowing mobility is investigated. It is found that reverse segregation can significantly influence the flowing mobility and the flowing regimes in the front head of the granular body. A mechanical explanation of the segregation mechanism can be presented by a new dimensionless number, which is correlated with the contact force.

[1]  B. A. Wills,et al.  Mineral processing technology , 1979 .

[2]  Rolf Katzenbach,et al.  Rapid flow of dry granular materials down inclined chutes impinging on rigid walls , 2007 .

[3]  M. Kleinhans.  Sorting in grain flows at the lee side of dunes , 2004 .

[4]  G. G. Stokes.  On the Effect of the Internal Friction of Fluids on the Motion of Pendulums , 2009 .

[5]  Shu-San Hsiau,et al.  DEM simulation of particle mixing in a sheared granular flow , 2008 .

[6]  Troy Shinbrot,et al.  Spontaneous chaotic granular mixing , 1999, Nature.

[7]  R. Iverson,et al.  U. S. Geological Survey , 1967, Radiocarbon.

[8]  Michele Larcher,et al.  Rheological stratification in experimental free-surface flows of granular–liquid mixtures , 2005, Journal of Fluid Mechanics.

[9]  Julio M. Ottino,et al.  Regimes of segregation and mixing in combined size and density granular systems: an experimental study , 2005 .

[10]  A. Thornton,et al.  A theory for particle size segregation in shallow granular free-surface flows , 2005, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[11]  J. Gray,et al.  Granular flow in partially filled slowly rotating drums , 2001, Journal of Fluid Mechanics.

[12]  Hehua Zhu,et al.  Two-Dimensional Discrete Element Theory for Rough Particles , 2009 .

[13]  S. Savage,et al.  The Mechanics of Rapid Granular Flows , 1984 .

[14]  J. Jenkins,et al.  A theory for the rapid flow of identical, smooth, nearly elastic, spherical particles , 1983, Journal of Fluid Mechanics.

[15]  R. Bagnold.  Experiments on a gravity-free dispersion of large solid spheres in a Newtonian fluid under shear , 1954, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[16]  S. Savage,et al.  The motion of a finite mass of granular material down a rough incline , 1989, Journal of Fluid Mechanics.

[17]  S. Savage,et al.  Particle Segregation in Granular Flows Down Chutes , 2000 .

[18]  S. Savage,et al.  Particle size segregation in inclined chute flow of dry cohesionless granular solids , 1988, Journal of Fluid Mechanics.

[19]  Yongqi Wang,et al.  Granular Material Theories Revisited , 2001 .

[20]  Charles S. Campbell,et al.  RAPID GRANULAR FLOWS , 1990 .

[21]  I. Goldhirsch,et al.  RAPID GRANULAR FLOWS , 2003 .

[22]  K. Hutter.  Continuum mechanics in environmental sciences and geophysics , 1993 .

[23]  Berend Smit,et al.  Commensurate ‘freezing’ of alkanes in the channels of a zeolite , 1995 .

[24]  Hai-Sui Yu,et al.  A novel discrete model for granular material incorporating rolling resistance , 2005 .

[25]  C. Prisco,et al.  A rheological model for the description of boulder impacts on granular strata , 2006 .

[26]  S. Savage.  Mechanics of Granular Flows , 1993 .

[27]  B. Zanuttigh,et al.  Instability and surge development in debris flows , 2007 .

[28]  J. Gray,et al.  Particle-size segregation and diffusive remixing in shallow granular avalanches , 2006, Journal of Fluid Mechanics.

[29]  Bernhard Peters,et al.  An approach to simulate the motion of spherical and non-spherical fuel particles in combustion chambers , 2001 .

[30]  Yutaka Tsuji,et al.  Lagrangian numerical simulation of plug flow of cohesionless particles in a horizontal pipe , 1992 .