Incipient sediment transport for non-cohesive landforms by the discrete element method (DEM)

Bravo, R.; Ortiz, P.; Pérez-Aparicio, José L.

doi:10.1016/j.apm.2013.08.010

Cited by 18 publications

(9 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mean flow entrainment models derive a transport initiation threshold Shields number from a force balance, and/or torque balance, between mean fluid forces and resisting contact forces acting on a representative particle resting on the bed surface (Agudo et al, 2017;Ali & Dey, 2016;Bagnold, 1936Bagnold, , 1941Bravo et al, 2014Bravo et al, , 2017Claudin & Andreotti, 2006;Dey, 1999Dey, , 2003Dey & Papanicolaou, 2008;Duan et al, 2013;Durán et al, 2011;Edwards & Namikas, 2015;He & Ohara, 2017;Iversen et al, 1976Iversen et al, , 1987Iversen & White, 1982;Lee et al, 2012;Lehning et al, 2000;Ling, 1995;Lu et al, 2005;Luckner & Zanke, 2007;Recking, 2009;Rousar et al, 2016;Schmidt, 1980;Shao & Lu, 2000;Vollmer & Kleinhans, 2007;Ward, 1969;Wiberg & Smith, 1987;White, 1940;Wu & Chou, 2003). Many of these models have been proposed to reproduce the Shields diagram, which displays two kinds of fluvial thresholds: a threshold obtained from extrapolating measurements of the transport rate to (nearly) vanishing transport and visual measurements of the initiation threshold of individual transport (see section 4.3 for details).…”

Section: Comparison With Previous Threshold Models 441 Mean Flow Ementioning

confidence: 99%

The Cessation Threshold of Nonsuspended Sediment Transport Across Aeolian and Fluvial Environments

2018

View full text Add to dashboard Cite

Using particle‐scale simulations of nonsuspended sediment transport for a large range of Newtonian fluids driving transport, including air and water, we determine the bulk transport cessation threshold normalΘtr by extrapolating the transport load as a function of the dimensionless fluid shear stress (Shields number) Θ to the vanishing transport limit. In this limit, the simulated steady states of continuous transport can be described by simple analytical model equations relating the average transport layer properties to the law of the wall flow velocity profile. We use this model to calculate normalΘtr for arbitrary environments and derive a general Shields‐like threshold diagram in which a Stokes‐like number replaces the particle Reynolds number. Despite the simplicity of our hydrodynamic description, the predicted cessation threshold, both from the simulations and analytical model, quantitatively agrees with measurements for transport in air and viscous and turbulent liquids despite not being fitted to these measurements. We interpret the analytical model as a description of a continuous rebound motion of transported particles and thus normalΘtr as the minimal fluid shear stress needed to compensate the average energy loss of transported particles during an average rebound at the bed surface. This interpretation, supported by simulations near normalΘtr, implies that entrainment mechanisms are needed to sustain transport above normalΘtr. While entrainment by turbulent events sustains intermittent transport, entrainment by particle‐bed impacts sustains continuous transport. Combining our interpretations with the critical energy criterion for incipient motion by Valyrakis and coworkers, we put forward a new conceptual picture of sediment transport intermittency.

show abstract

Section: Comparison With Previous Threshold Models 441 Mean Flow Ementioning

confidence: 99%

The Cessation Threshold of Nonsuspended Sediment Transport Across Aeolian and Fluvial Environments

2018

View full text Add to dashboard Cite

show abstract

“…Many experimental approaches have been applied to determine the threshold for the onset of motion. The studies include parameters such as the particle Reynolds number 13,16,17,18,19,20 , the relative flow submergence 21,22,23,24 or geometrical factors as the angle of repose 16,18,25 , exposure to the flow 26,27,28,29 , relative grain protrusion 29 or streamwise bed slope 30 .…”

Section: Introductionmentioning

confidence: 99%

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Agudo

Han

Park

et al. 2018

JoVE

View full text Add to dashboard Cite

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to turbulent flow conditions are presented. For that purpose, the incipient motion of a single bead is studied on regular substrates that consist of a monolayer of fixed spheres of uniform size that are regularly arranged in triangular and quadratic symmetries. The threshold is characterized by the critical Shields number. The criterion for the onset of motion is defined as the displacement from the original equilibrium position to the neighboring one. The displacement and the mode of motion are identified with an imaging system. The laminar flow is induced using a rotational rheometer with a parallel disk configuration. The shear Reynolds number remains below 1. The turbulent flow is induced in a low-speed wind tunnel with open jet test section. The air velocity is regulated with a frequency converter on the blower fan. The velocity profile is measured with a hot wire probe connected to a hot film anemometer. The shear Reynolds number ranges between 40 and 150. The logarithmic velocity law and the modified wall law presented by Rotta are used to infer the shear velocity from the experimental data. The latter is of special interest when the mobile bead is partially exposed to the turbulent flow in the so-called hydraulically transitional flow regime. The shear stress is estimated at onset of motion. Some illustrative results showing the strong impact of the angle of repose, and the exposure of the bead to shear flow are represented in both regimes.

show abstract

“…The suspension density is numerically computed by DEM following the same procedure described for the previous test and Eq. (20). Again, to reduce the CPU cost, the sphere is not simulated as an additional particle for the same reasons as we did not simulate the hydrometer in the ASTM test.…”

Section: Simulation Of the Buoyancy Testmentioning

confidence: 99%

“…Once the depth of the tip of the hydrometer is known, the depth of its center of gravity is computed, and the density of the solution is obtained using (20) considering a single layer extending the height of the bulb. From these two parameters, the pairs (φ o , w o ) are obtained as in the standard.…”

Section: Simulation Of the Astm-d422 Hydrometer Testmentioning

confidence: 99%

“…This technique substantially reduces computation, considering that flow does modify particle movement but particles do not substantially modify flow: see [20] for the application of this technique to the analysis of inclined sediment beds. The assumption is acceptable to simulate sedimentation of finegrained materials due to the small size and low deposition velocities of the particles.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Numerical sedimentation particle-size analysis using the Discrete Element Method

Bravo

Pérez-Aparicio

Gómez‐Hernández

2015

Advances in Water Resources

Self Cite

View full text Add to dashboard Cite

Sedimentation processes are generally modelled using an equivalent continuum approach based on the coupling of the Navier-Stokes and the advection-dispersion equations; the sediment concentration within an elementary fluid volume is the variable of interest. Continuous advances in computational capabilities have brought up a new type of modelling that simulates the individual motion and contact interactions of grains: the Discrete Element Method (DEM). In this work, DEM interacts with the simulation of flow using the well known one-way-coupling method, a computationally affordable approach for the time-consuming numerical simulation of the ASTM-D422, buoyancy and pipette sedimentation tests. These tests are used in the laboratory to determine the particle-size distribution of fine-grained aggregates. Five samples with different particle-size distributions are modelled by about six million rigid spheres projected on two-dimensions, with diameters ranging from 2.5 × 10 −6 m to 70 × 10 −6 m, forming a water suspension in a sedimentation cylinder. DEM simulates the particle's movement considering laminar flow interactions of hydrostatic thrust, drag and lubrication forces. The simulation provides the temporal/spatial distributions of densities and concentrations of the suspension.The numerical simulation cannot replace the laboratory tests since it needs the final granulometry as initial data; but, as the results show, these simulations can identify the strong and weak points of each method and eventually recommend useful variations and draw conclusions on their validity, aspects very difficult to achieve in the laboratory.

show abstract

Incipient sediment transport for non-cohesive landforms by the discrete element method (DEM)

Cited by 18 publications

References 22 publications

The Cessation Threshold of Nonsuspended Sediment Transport Across Aeolian and Fluvial Environments

The Cessation Threshold of Nonsuspended Sediment Transport Across Aeolian and Fluvial Environments

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Numerical sedimentation particle-size analysis using the Discrete Element Method

Contact Info

Product

Resources

About