Numerical Simulation of Jamming Transition in Granular System Under Cyclic Compression Using Smooth Particle Hydrodynamics

2016 ◽  
Author(s):  
Raihan Tayeb ◽  
Yijin Mao ◽  
Yuwen Zhang
Keyword(s):  
Granular Materials ◽  
Coordination Number ◽  
Packing Fraction ◽  
Granular System ◽  
Smooth Particle Hydrodynamics ◽  
Stable States ◽  
Jamming Transition ◽  
Cyclic Compression ◽  
Particle Hydrodynamics ◽  
Number Of Cycles

The jamming of granular materials, which indicates how disordered particle systems change from mechanically unstable to stable states, has attracted significant recent interest due, but not limited, to the appearance of jamming transition or similar behavior in a broad variety of systems. Recent experiments on jamming transition have revealed the relationship between mean coordination number and packing fraction for different jammed states. In this paper the jamming states of two dimensional granular materials under cyclic compression using Smooth Particle Hydrodynamics (SPH) approach is numerically investigated. The SPH method allows one to study the stress developed within individual granular particles of arbitrary shape. In this study the granular system is cyclically and isotropically compressed or expanded. The system undergoes a range of jamming states over a large number of cycles. We measure the evolution of global pressure, mean coordination number, and packing fraction. The force chains and probability density function of force for different compression cycles are also investigated.

scholarly journals Estimating Contact Force Chains Using Artificial Neural Network

2021 ◽  
Vol 11 (14) ◽  
pp. 6278
Author(s):  
Mengmeng Wu ◽  
Jianfeng Wang
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Particle Size ◽  
Granular Materials ◽  
Coordination Number ◽  
Contact Force ◽  
Force Chains ◽  
Granular System ◽  
Biaxial Test ◽  
Artificial Neural

The inhomogeneous distribution of contact force chains (CFC) in quasi-statically sheared granular materials dominates their bulk mechanical properties. Although previous micromechanical investigations have gained significant insights into the statistical and spatial distribution of CFC, they still lack the capacity to quantitatively estimate CFC evolution in a sheared granular system. In this paper, an artificial neural network (ANN) based on discrete element method (DEM) simulation data is developed and applied to predict the anisotropy of CFC in an assembly of spherical grains undergoing a biaxial test. Five particle-scale features including particle size, coordination number, x- and y-velocity (i.e., x and y-components of the particle velocity), and spin, which all contain predictive information about the CFC, are used to establish the ANN. The results of the model prediction show that the combined features of particle size and coordination number have a dominating influence on the CFC’s estimation. An excellent model performance manifested in a close match between the rose diagrams of the CFC from the ANN predictions and DEM simulations is obtained with a mean accuracy of about 0.85. This study has shown that machine learning is a promising tool for studying the complex mechanical behaviors of granular materials.

scholarly journals A parameter-free total Lagrangian smooth particle hydrodynamics algorithm applied to problems with free surfaces

2021 ◽  
Author(s):  
Kenny W. Q. Low ◽  
Chun Hean Lee ◽  
Antonio J. Gil ◽  
Jibran Haider ◽  
Javier Bonet
Keyword(s):  
Ad Hoc ◽  
Wide Spectrum ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Point Of View ◽  
Numerical Dissipation ◽  
Lagrangian Description ◽  
Smooth Particle Hydrodynamics ◽  
Particle Hydrodynamics ◽  
Sph Algorithm

AbstractThis paper presents a new Smooth Particle Hydrodynamics computational framework for the solution of inviscid free surface flow problems. The formulation is based on the Total Lagrangian description of a system of first-order conservation laws written in terms of the linear momentum and the Jacobian of the deformation. One of the aims of this paper is to explore the use of Total Lagrangian description in the case of large deformations but without topological changes. In this case, the evaluation of spatial integrals is carried out with respect to the initial undeformed configuration, yielding an extremely efficient formulation where the need for continuous particle neighbouring search is completely circumvented. To guarantee stability from the SPH discretisation point of view, consistently derived Riemann-based numerical dissipation is suitably introduced where global numerical entropy production is demonstrated via a novel technique in terms of the time rate of the Hamiltonian of the system. Since the kernel derivatives presented in this work are fixed in the reference configuration, the non-physical clumping mechanism is completely removed. To fulfil conservation of the global angular momentum, a posteriori (least-squares) projection procedure is introduced. Finally, a wide spectrum of dedicated prototype problems is thoroughly examined. Through these tests, the SPH methodology overcomes by construction a number of persistent numerical drawbacks (e.g. hour-glassing, pressure instability, global conservation and/or completeness issues) commonly found in SPH literature, without resorting to the use of any ad-hoc user-defined artificial stabilisation parameters. Crucially, the overall SPH algorithm yields equal second order of convergence for both velocities and pressure.

scholarly journals Formation of Prestellar Cores via Non-Isothermal Gas Fragmentation

2015 ◽  
Vol 32 ◽  
Author(s):  
S. Anathpindika
Keyword(s):  
Gravitational Instability ◽  
Gas Flows ◽  
Smooth Particle Hydrodynamics ◽  
Three Phase ◽  
Prestellar Cores ◽  
Particle Hydrodynamics ◽  
Unstable Medium ◽  
Stage Process ◽  
Isothermal Gas ◽  
Gas Accretion

AbstractSheet-like clouds are common in turbulent gas and perhaps form via collisions between turbulent gas flows. Having examined the evolution of an isothermal shocked slab in an earlier contribution, in this work we follow the evolution of a sheet-like cloud confined by (thermal) pressure and gas in it is allowed to cool. The extant purpose of this endeavour is to study the early phases of core-formation. The observed evolution of this cloud supports the conjecture that molecular clouds themselves are three-phase media (comprising viz. a stable cold and warm medium, and a third thermally unstable medium), though it appears, clouds may evolve in this manner irrespective of whether they are gravitationally bound. We report, this sheet fragments initially due to the growth of the thermal instability (TI) and some fragments are elongated, filament-like. Subsequently, relatively large fragments become gravitationally unstable and sub-fragment into smaller cores. The formation of cores appears to be a three stage process: first, growth of the TI leads to rapid fragmentation of the slab; second, relatively small fragments acquire mass via gas-accretion and/or merger and third, sufficiently massive fragments become susceptible to the gravitational instability and sub-fragment to form smaller cores. We investigate typical properties of clumps (and smaller cores) resulting from this fragmentation process. Findings of this work support the suggestion that the weak velocity field usually observed in dense clumps and smaller cores is likely seeded by the growth of dynamic instabilities. Simulations were performed using the smooth particle hydrodynamics algorithm.

scholarly journals Modelling Closed-Die Forging Operations Using Total Lagrangian Smooth Particle Hydrodynamics

2019 ◽  
Author(s):  
Anthony Manson
Keyword(s):  
Large Deformation ◽  
Smooth Particle Hydrodynamics ◽  
Material Flows ◽  
Forging Process ◽  
Mesh Free ◽  
Closed Die Forging ◽  
Particle Hydrodynamics ◽  
Mesh Free Method ◽  
Large Material ◽  
Simulation Parameters

Total Lagrangian Smooth Particle Hydrodynamics (TLSPH) has been applied to a set of non-trivial, commercially interesting forging examples.Being a mesh-free method, TLSPH can conveniently simulate processes having large deformation and material separation.Test cases were designed that were characterized by large material flows having large changes in grain connectivity.The implementation used, Smooth Mach Dynamics (SMD), provided tunable simulation parameters that enabled the simulation to optimally match each case.The results showed that the TLSPH/SMD has the potential to model the metal forging process efficiently without numerical instabilities.Each case studied required adaptation of the simulation parameters to optimize the results.

scholarly journals Simulation of Bullet Fragmentation and Penetration in Granular Media

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5243
Author(s):  
Froylan Alonso Soriano-Moranchel ◽  
Juan Manuel Sandoval-Pineda ◽  
Guadalupe Juliana Gutiérrez-Paredes ◽  
Usiel Sandino Silva-Rivera ◽  
Luis Armando Flores-Herrera
Keyword(s):  
Kinetic Energy ◽  
Granular Media ◽  
Elastic Collision ◽  
Smooth Particle Hydrodynamics ◽  
X Ray ◽  
Bullet Fragmentation ◽  
Particle Hydrodynamics ◽  
The Moment ◽  
Physical Phenomena ◽  
The Impact

The aim of this work is to simulate the fragmentation of bullets impacted through granular media, in this case, sand. In order to validate the simulation, a group of experiments were conducted with the sand contained in two different box prototypes. The walls of the first box were constructed with fiberglass and the second with plywood. The prototypes were subjected to the impact force of bullets fired 15 m away from the box. After the shots, X-ray photographs were taken to observe the penetration depth. Transient numerical analyses were conducted to simulate these physical phenomena by using the smooth particle hydrodynamics (SPH) module of ANSYS® 2019 AUTODYN software. Advantageously, this module considers the granular media as a group of uniform particles capable of transferring kinetic energy during the elastic collision component of an impact. The experimental results demonstrated a reduction in the maximum bullet kinetic energy of 2750 J to 100 J in 0.8 ms. The numerical results compared with the X-ray photographs showed similar results demonstrating the capability of sand to dissipate kinetic energy and the fragmentation of the bullet caused at the moment of impact.

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