The elementary mechanisms driving the ubiquitous surface erosion of cohesive geomaterials can be analysed from a micromechanical perspective combining well-known numerical techniques. Here, a coupled model combining the Discrete Element and Lattice Boltzmann methods (DEM-LBM) provides an insight into the solid-fluid interaction during the transient erosion caused by a vertical fluid jet impinging on the surface of a granular assembly. The brittle cementation providing cohesion between the solid grains is described here by means of a simple bond model with a single-parameter yield surface. The initial topology of the surface erosion tends to mimic the profile of fluid velocity directly above the soil surface. We find that both the rate of erosion and the magnitude of eroded mass depend directly on the micromechanical strength of the single solid bonds.

JF - IV International Conference on Particle-based Methods (PARTICLES 2015) PB - International Center for Numerical Methods in Engineering (CIMNE) CY - SEP 28-30 2015 Barcelona, SPAIN VL - PARTICLE-BASED METHODS IV-FUNDAMENTALS AND APPLICATIONS UR - https://hal.archives-ouvertes.fr/hal-01269324 ER - TY - Generic T1 - Transient regime to fluidized chimney within a granular bed by means of a 2D DEM/LBM modeling T2 - IV International Conference on Particle-based Methods (PARTICLES 2015) Y1 - 2015 A1 - Jeff Ngoma A1 - Pierre Philippe A1 - Stéphane Bonelli A1 - Cuellar, Pablo A1 - Jean-Yves Delenne A1 - Farhang Radjaï ED - Onate, E ED - Bischoff, M ED - Owen, DRJ KW - DEM KW - Fluidization KW - Granular Materials KW - LBM AB -Beyond a given threshold, an upward fluid flow at constant flowrate, injected through a small size section, is able to generate a fluidization along a vertical chimney over the entire height of a granular assembly. Fluidization is first initiated in the immediate vicinity of the injection hole and then the fluidized zone grows gradually until reaching the upper surface of the granular packing. In this work, we present numerical results on the kinetics of chimney fluidization in an immersed granular bed produced with two-dimensional simulations coupling the Discrete Element and Lattice Boltzmann Methods (DEM-LBM). A parametric study is carried out with 11 different sets of physical parameters and analyzed based on spatio-temporal diagrams. Then a dimensional analysis allows finding general scaling laws for both threshold and growth rate of the fluidized zone by use of two dimensionless numbers, namely Reynolds and Archimedes numbers, while quite simple empirical relationships can also be proposed.

JF - IV International Conference on Particle-based Methods (PARTICLES 2015) PB - International Center for Numerical Methods in Engineering (CIMNE) CY - SEP 28-30 2015 Barcelona, SPAIN VL - PARTICLE-BASED METHODS IV-FUNDAMENTALS AND APPLICATIONS UR - https://hal.archives-ouvertes.fr/hal-01269325 ER -