Particle dynamics in dense shear granular flow

Wang, Dengming; Zhou, Youhe

doi:10.1007/s10409-009-0322-y

Cited by 14 publications

(6 citation statements)

References 29 publications

(57 reference statements)

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“…In rotating drum experiments with natural debris‐flow mixtures, Hsu [] also found that distributions of basal force were well described by generalized Pareto distributions with

\overset{k}{true}

between ∼0.0–0.3. In contrast to these results, laboratory experiments and simulations with monodispersed granular flows find that contact forces in the tail are distributed in an exponential manner [e.g., Howell et al , ; Longhi et al , ; Ferguson et al , ; Jalali et al , ; Gardel et al , ; Kheiripour Langroudi et al , ; Bardenhagen et al , ; Antony , ; O'Hern et al , ; Lois et al , ; Wang and Zhou , ]. Exponential distributions estimated from our field measurements under‐predict the probability of large magnitude fluctuations by orders of magnitude (Figure ).…”

Section: Discussionmentioning

confidence: 99%

Field measurement of basal forces generated by erosive debris flows

et al. 2013

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[1] It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24 cm by 15.24 cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris-flow events that incised bedrock. Over the 4 year monitoring period, 11 debris-flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm. The basal force during these erosive debris-flow events had a large-magnitude (up to 21 kN, which was approximately 50 times larger than the concurrent time-averaged mean force), high-frequency (greater than 1 Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time-averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than 20 times the median bed sediment grain size, no significant fluctuations about the time-averaged mean force were measured, indicating that a thin layer of sediment ( 5 cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse-grained granular surges and water-rich, intersurge flow had very similar basal force distributions despite differences in appearance and bulk-flow density. These results demonstrate that debris flows can have strong control on rates of steepland evolution and contribute to a foundation needed for modeling debris-flow incision stochastically.

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“…In rotating drum experiments with natural debris‐flow mixtures, Hsu [] also found that distributions of basal force were well described by generalized Pareto distributions with

\overset{k}{true}

Section: Discussionmentioning

confidence: 99%

Field measurement of basal forces generated by erosive debris flows

et al. 2013

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“…Due to its natural treatment at a particle length scale, recent discrete element method (DEM) [24][25][26][27] has shown its capability to study the effect of rearrangement not only in macroscopic aspects, such as densification rates [24,26,28], viscosities [26,29], anisotropic sintering [30], constrained sintering [31], but also in microscopic aspect of crack evolution during sintering [26,32]. This method has also shed some lights on our understanding of certain problems about agglomerates.…”

Section: Introductionmentioning

confidence: 99%

Factors influencing particle agglomeration during solid-state sintering

Wang

Chen

2012

Acta Mech Sin

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Discrete element method (DEM) is used to study the factors affecting agglomeration in three-dimensional copper particle systems during solid-state sintering. A new parameter is proposed to characterize agglomeration. The effects of a series of factors are studied, including particle size, size distribution, inter-particle tangential viscosity, temperature, initial density and initial distribution of particles on agglomeration. We find that the systems with smaller particles, broader particle size distribution, smaller viscosity, higher sintering temperature and smaller initial density have stronger particle agglomeration and different distributions of particles induce different agglomerations. This study should be very useful for understanding the phenomenon of agglomeration and the micro-structural evolution during sintering and guiding sintering routes to avoid detrimental agglomeration.

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“…In the present simulation, we take β = 10 8 and the time step is 0.2 s. The concept of affine transformation which has been used in literatures [7,13,29,30] is not adopted in our simulations because of the strong restriction of rearrangement of particles as pointed out by Olmos [31]. The method used in the present paper is just like the one used in the original DEM work by Cundall [32] and in the granular study [33].…”

Section: Discrete Element Methodsmentioning

confidence: 99%

The effect of agglomerate on micro-structural evolution in solid-state sintering

Wang

Chen

2012

Acta Mech Sin

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Discrete element method (DEM) is used in the present paper to simulate the microstructural evolution of a planar layer of copper particles during sintering. Formation of agglomerates and the effect of their rearrangement on densification are mainly focused on. Comparing to the existing experimental observations, we find that agglomerate can form spontaneously in sintering and its rearrangement could accelerate the densification of compacts. Snapshots of numerical simulations agree qualitatively well with experimental observations. The method could be readily extended to investigate the effect of agglomerate on sintering in a threedimensional model, which should be very useful for understanding the evolution of microstructure of sintering systems.

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Particle dynamics in dense shear granular flow

Cited by 14 publications

References 29 publications

Field measurement of basal forces generated by erosive debris flows

Field measurement of basal forces generated by erosive debris flows

Factors influencing particle agglomeration during solid-state sintering

The effect of agglomerate on micro-structural evolution in solid-state sintering

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