Optimal description of two-dimensional complex-shaped objects using spheropolygons

Dobrohotoff, Peter; Azeezullah, S. I.; Maggi, Federico; Alonso‐Marroquín, Fernando

doi:10.1007/s10035-012-0357-9

Cited by 15 publications

(4 citation statements)

References 15 publications

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“…Details of the algorithm can be found in Refs. [34,35]. At the end the image was scaled to reflect a typical sternum dimensions of 200 × 460 mm 2 .…”

Section: A Shape Representationmentioning

confidence: 99%

Simulation of counterflow pedestrian dynamics using spheropolygons

et al. 2014

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Pedestrian dynamic models are typically designed for comfortable walking or slightly congested conditions and typically use a single disk or combination of three disks for the shape of a pedestrian. Under crowd conditions, a more accurate pedestrian shape has advantages over the traditional single or three-disks model. We developed a method for simulating pedestrian dynamics in a large dense crowd of spheropolygons adapted to the cross section of the chest and arms of a pedestrian. Our numerical model calculates pedestrian motion from Newton's second law, taking into account viscoelastic contact forces, contact friction, and ground-reaction forces. Ground-reaction torque was taken to arise solely from the pedestrians' orientation toward their preferred destination. Simulations of counterflow pedestrians dynamics in corridors were used to gain insight into a tragic incident at the Madrid Arena pavilion in Spain, where five girls were crushed to death. The incident took place at a Halloween Celebration in 2012, in a long, densely crowded hallway used as entrance and exit at the same time. Our simulations reconstruct the mechanism of clogging in the hallway. The hypothetical case of a total evacuation order was also investigated. The results highlights the importance of the pedestrians' density and the effect of counterflow in the onset of avalanches and clogging and provides an estimation of the number of injuries based on a calculation of the contact-force network between the pedestrians.

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“…Details of the algorithm can be found in Refs. [34,35]. At the end the image was scaled to reflect a typical sternum dimensions of 200 × 460 mm 2 .…”

Section: A Shape Representationmentioning

confidence: 99%

Simulation of counterflow pedestrian dynamics using spheropolygons

et al. 2014

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“…Moreover, these techniques cannot effectively simulate highly irregular shape grains characterized by a variety of internal voids and vesicles. Similar challenges are represented by other less common approaches for capturing complex granular shapes, including superquadric elements (Cleary et al, 1997;Williams & Pentland, 1992), spheropolygons (Dobrohotoff et al, 2012), and the nonuniform rational basis splines (Andrade et al, 2012).…”

Section: Introductionmentioning

confidence: 87%

Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains: Effects of Grain Shapes on the Mechanical Behaviors

2019

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One of the challenges to overcome in Moon mining operations, such as soil handling, drilling, excavation, and wheeled movement, is understanding the mechanical behaviors of lunar soil, which is composed of grains characterized by highly irregular shapes. The impracticality of performing mechanical experiments on lunar soil samples has made computational techniques useful for exploring the mechanical behaviors of lunar soil. This paper uses particle flow code and describes a procedure for simulating lunar soil grains with specific size, shape, and strength distributions. We adopt data from soil samples 64501 and 60501 retrieved in Apollo 16. Lunar soil samples are simulated as assemblies of different shapes of grains consisting of rigid spheres connected through parallel bonds. We classify grains into four categories based on their shape: agglutinate, breccia A, breccia B, and plagioclase. We simulate each grain based on available imaging studies on their shape characteristics. We reveal the significance of grain shape irregularity through angle‐of‐repose tests on samples with and without irregularly shaped agglutinates. Results show that the shape irregularity increases the angle of repose by 6°. We repeat the test under different gravitational acceleration ranging from 0.1 to 25 m/s2 and show that for values below about 10 m/s2, the angle of repose is inversely related to the gravity but above 10 m/s2, remains independent of the gravity. We perform triaxial compression tests to investigate behaviors of simulated samples under confined loadings. The confinement varies from zero to 15 kPa, corresponding to the lateral in situ stress at depths up to 250 cm. The cohesion and friction angle derived from the triaxial tests are shown to agree with the lab and in situ measurements. This numerical practice and presented methodology pave the way for full‐scale simulation of mining operations on the Moon surface.

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“…The gravel consists of nonspherical particles with a sphericity between 0.35 and 0.87 (average: 0.75) and an aspect ratio between 1.06 and 2.49 (average: 1.49) which is both obtained by an image analysis. To represent such particles, various methods can be applied [17,18,21]. For this approximation a genetic algorithm which is part of Matlab is used.…”

Section: Shape Approximationmentioning

confidence: 99%

“…Additionally, Dobrohotoff et al [18] used spheropolygons to describe two-dimensional complex-shaped objects like pebbles, gravel and crushed shells where only a few iteration 3 steps were needed to get good results. The significant optimization of the shape was confirmed by comparing anchor pull-out and hopper discharge simulations with respective experiments.…”

Section: Introductionmentioning

confidence: 99%

A strategy to determine DEM parameters for spherical and non-spherical particles

et al. 2017

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In Discrete Element Method (DEM) simulations the choice of appropriate contact parameters is significant to obtain reasonable results. Particularly, for the determination of DEM parameters for non-spherical particles a general straightforward procedure is not available. Therefore, in a first step of the investigation here, methods to obtain the friction and restitution coefficients experimentally for single particles (Polyoxymethylene (POM) spheres and quartz gravel) will be introduced. In the following, these predetermined DEM coefficients are used as initial values for the adjustment of bulk simulations to respective experiments. In the DEM simulations, the quartz gravel particles are represented by non-spherical particles approximated by clustered spheres. The best fit approximation of the non-spherical particles is performed automatically by a genetic algorithm. In order to optimize the sliding and rolling friction coefficients for DEM simulations, the static and dynamic angle of repose are determined from granular piles obtained by slump tests and rotating drum experiments, respectively. Additionally, a vibrating plate is used to obtain the dynamic bed height which is mainly influenced by the coefficient of restitution. The adjustment of the results of the bulk simulations to the experiments is conducted automatically by an optimization tool based on a genetic algorithm. The obtained contact parameters are later used to perform batch-screening DEM simulations and lead to accurate results. This underlines the applicability of the in parts automated strategy to obtain DEM parameters for particulate processes like screening.

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Optimal description of two-dimensional complex-shaped objects using spheropolygons

Cited by 15 publications

References 15 publications

Simulation of counterflow pedestrian dynamics using spheropolygons

Simulation of counterflow pedestrian dynamics using spheropolygons

Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains: Effects of Grain Shapes on the Mechanical Behaviors

A strategy to determine DEM parameters for spherical and non-spherical particles

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