Granular Flow: From Dilute to Jammed States

AbstractGranular flows of angular rock fragments such as rock avalanches and dense pyroclastic flows are simulated numerically by means of the discrete element method. Since large-scale flows generate stresses that are larger than those generated by small-scale flows, the purpose of these simulations is to understand the effect that the stress level has on flow mobility. The results show that granular flows that slide en mass have a flow mobility that is not influenced by the stress level. On the contrary, the stress level governs flow mobility when granular flow dynamics is affected by clast agitation and collisions. This second case occurs on a relatively rougher subsurface where an increase of the stress level causes an increase of flow mobility. The results show also that as the stress level increases, the effect that an increase of flow volume has on flow mobility switches sign from causing a decrease of mobility at low stress level to causing an increase of mobility at high stress level. This latter volume effect corresponds to the famous Heim’s mobility increase with the increase of the volume of large rock avalanches detected so far only in the field and for this reason considered inexplicable without resorting to extraordinary mechanisms. Granular flow dynamics is described in terms of dimensionless scaling parameters in three different granular flow regimes. This paper illustrates for each regime the functional relationship of flow mobility with stress level, flow volume, grain size, channel width, and basal friction.

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Numerical analysis of the drag on a rigid body in an immersed granular flow

Computational Particle Mechanics ◽

10.1007/s40571-021-00418-w ◽

2021 ◽

Author(s):

Nathan Coppin ◽

Matthieu Constant ◽

Jonathan Lambrechts ◽

Frédéric Dubois ◽

Vincent Legat

Keyword(s):

Numerical Analysis ◽

Rigid Body ◽

Granular Flow

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Silo music and silo quake: granular flow-induced vibration

Powder Technology ◽

10.1016/j.powtec.2004.07.003 ◽

2004 ◽

Vol 145 (3) ◽

pp. 190-202 ◽

Cited By ~ 34

Author(s):

Benson K. Muite ◽

Shandon F. Quinn ◽

Sankaran Sundaresan ◽

K. Kesava Rao

Keyword(s):

Granular Flow ◽

Flow Induced Vibration

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A Convex Complementarity Approach for Simulating Large Granular Flows

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4001371 ◽

2010 ◽

Vol 5 (3) ◽

Cited By ~ 22

Author(s):

Alessandro Tasora ◽

Mihai Anitescu

Keyword(s):

Granular Flow ◽

Complementarity Problems ◽

Particle Interaction ◽

Granular Flows ◽

Rigid Bodies ◽

Integration Time ◽

Frictional Contacts ◽

Physical Experiments ◽

Dense Granular Flow ◽

Number Of Particles

Aiming at the simulation of dense granular flows, we propose and test a numerical method based on successive convex complementarity problems. This approach originates from a multibody description of the granular flow: all the particles are simulated as rigid bodies with arbitrary shapes and frictional contacts. Unlike the discrete element method (DEM), the proposed approach does not require small integration time steps typical of stiff particle interaction; this fact, together with the development of optimized algorithms that can run also on parallel computing architectures, allows an efficient application of the proposed methodology to granular flows with a large number of particles. We present an application to the analysis of the refueling flow in pebble-bed nuclear reactors. Extensive validation of our method against both DEM and physical experiments results indicates that essential collective characteristics of dense granular flow are accurately predicted.

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