Validation of DEM prediction for granular avalanches on irregular terrain

Mead, Stuart; Cleary, Paul W.

doi:10.1002/2014jf003331

Cited by 34 publications

(16 citation statements)

References 79 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This reaffirms the point that porosity alone is not an adequate measure of system rheology. For example, Mead and Cleary [] demonstrated that modeling granular avalanches could only replicate natural examples if nonspherical particles were used. Yamamoto and Matsuoka [] and Kawabata et al .…”

Section: The Dynamics Of Hydrogranular Mediasupporting

confidence: 86%

“…This reaffirms the point that porosity alone is not an adequate measure of system rheology. For example, Mead and Cleary [2015] demonstrated that modeling granular avalanches could only replicate natural examples if nonspherical particles were used. Yamamoto and Matsuoka [1997] and Kawabata et al [2013] demonstrated how plate-like particles, a common shape of natural crystals, leads to distinct microstructures, shear banding, and kinematic features reminiscent of geological examples.…”

Section: Nonspherical Particlesmentioning

confidence: 99%

See 1 more Smart Citation

On the kinematics and dynamics of crystal‐rich systems

2017

View full text Add to dashboard Cite

Partially molten rocks, often called a mush, are examples of a hydrogranular mixture where the dynamics are controlled by both fluid and crystal‐crystal interactions. An obstacle to progress in understanding high‐temperature hydrogranular systems has been the lack of adequate levels of description of microphysical processes. Here we rationalize the hydrogranular kinematic and dynamic states by applying the concept of particle (crystal) force chains. We exemplify this with discrete‐element computational fluid dynamic simulations of the intrusion of a basaltic melt into an olivine‐basalt mush, where crystal‐scale force chains, crystal transport, and melt mixing are resolved. To describe the microscale kinematics of the system, we introduce the coordination number and the fabric tensors of particle contacts and forces. We quantify the changing contact and force fabric anisotropy, coaxiality, and the connectedness of the mush, under dynamic conditions. To describe the dynamics, particle and fluid characteristic response times are derived. These are used to define local and bulk Stokes numbers, and viscous and inertia numbers, which quantify the multiphase coupling under crystal‐rich conditions. We employ the Sommerfeld number, which describes the importance of crystal‐melt lubrication, with a viscous number to illustrate the dynamic regimes of crystal‐rich magmas. We show that the notion of mechanical “lock up” is not uniquely identified with a particular crystal volume fraction and that distinct mechanical behaviors can emerge simultaneously within a crystal‐rich system. We also posit that this framework describes magmatic fabrics and processes which “unlock” a crystal mush prior to eruption or mixing.

show abstract

Section: The Dynamics Of Hydrogranular Mediasupporting

confidence: 86%

Section: Nonspherical Particlesmentioning

confidence: 99%

On the kinematics and dynamics of crystal‐rich systems

2017

View full text Add to dashboard Cite

show abstract

“…Conversely, models of geophysical flows that ignore their granular nature (such as multiphase and depthaveraged models) are unable to predict the flow runouts even with the correct parameter values. Studies of granular flows by means of discrete element modeling include Valentino et al (2008), Banton et al (2009), Girolami et al (2012, Yohannes et al (2012), Mollon et al (2012), Cagnoli and Piersanti (2015) and Mead and Cleary (2015).…”

Section: Introductionmentioning

confidence: 99%

“…These polyhedrons represent an equant, an oblate and a prolate particle, respectively. Nonspherical particles are preferred because when interacting amongst themselves and with the boundary surfaces, their energy dissipation mechanism (due to collisions and attrition) is comparable with that of natural fragments since they are both angular (Cagnoli and Romano, 2012a;Mead and Cleary, 2015). The proportion of each particle shape is always the same in all flows irrespective of grain size, flow mass or channel features: the equant particles are 38 %, the oblate particles 22 % and the prolate particles 40 % of the flow mass.…”

Section: Introductionmentioning

confidence: 99%

Combined effects of grain size, flow volume and channel width on geophysical flow mobility: three-dimensional discrete element modeling of dry and dense flows of angular rock fragments

Cagnoli

Piersanti

2017

Solid Earth

View full text Add to dashboard Cite

Abstract. We have carried out new three-dimensional numerical simulations by using a discrete element method (DEM) to study the mobility of dry granular flows of angular rock fragments. These simulations are relevant for geophysical flows such as rock avalanches and pyroclastic flows. The model is validated by previous laboratory experiments. We confirm that (1) the finer the grain size, the larger the mobility of the center of mass of granular flows; (2) the smaller the flow volume, the larger the mobility of the center of mass of granular flows and (3) the wider the channel, the larger the mobility of the center of mass of granular flows. The grain size effect is due to the fact that finer grain size flows dissipate intrinsically less energy. This volume effect is the opposite of that experienced by the flow fronts. The original contribution of this paper consists of providing a comparison of the mobility of granular flows in six channels with a different cross section each. This results in a new scaling parameter χ that has the product of grain size and the cubic root of flow volume as the numerator and the product of channel width and flow length as the denominator. The linear correlation between the reciprocal of mobility and parameter χ is statistically highly significant. Parameter χ confirms that the mobility of the center of mass of granular flows is an increasing function of the ratio of the number of fragments per unit of flow mass to the total number of fragments in the flow. These are two characteristic numbers of particles whose effect on mobility is scale invariant.

show abstract

“…This is simply untrue. The soft-particle discrete element technique has been tested against numerous laboratory experiments [e.g., Mead and Cleary, 2015]. (And while Iverson seems to have a high opinion of the Mead and Cleary simulations, their results merely show that discrete element model simulations can closely match one of Iverson's experiments; they reveal nothing about mechanics of long runout landslides.)…”

Section: Landslide Dynamics Testing Models and Diverse Datamentioning

confidence: 99%

Reply to comment by Iverson on “The reduction of friction in long runout landslides as an emergent phenomenon”

2016

View full text Add to dashboard Cite

Here we address the comments by Iverson (2016) on our recent work concerning the reduction of friction in long runout landslides. Iverson (2016) questions the veracity of our models and suggests that high basal pore fluid pressure is the dominant mechanism reducing friction in long runout landslides. The main goal of our work was to elucidate the mechanism responsible for the apparent reduction of friction and long runout occurring in the landslide simulations of Campbell et al. (1995), which did not include an interstitial fluid. We found that the apparent reduction of friction in large slides could be explained by acoustic waves causing sliding to preferentially occur at pressures below the expected overburden, a mechanism reminiscent of acoustic fluidization. Such a mechanism is required to explain the long runout of dry landslides such as those on the Moon and other airless or waterless bodies. While our models provide no estimates of the effect of fluids on landslide runout, we have demonstrated a mechanism that increases runout distances that does not involve fluids.

show abstract

Validation of DEM prediction for granular avalanches on irregular terrain

Cited by 34 publications

References 79 publications

On the kinematics and dynamics of crystal‐rich systems

On the kinematics and dynamics of crystal‐rich systems

Combined effects of grain size, flow volume and channel width on geophysical flow mobility: three-dimensional discrete element modeling of dry and dense flows of angular rock fragments

Reply to comment by Iverson on “The reduction of friction in long runout landslides as an emergent phenomenon”

Contact Info

Product

Resources

About