IV International Conference on Particle-Based Methods: fundamentals and applications (PARTICLES 2015) Barcelona, 28-30 September, 2015
http://hdl.handle.net/2117/187414
2022-05-19T17:38:12ZRegular or random: a discussion on SPH initial particle distribution
http://hdl.handle.net/2117/188302
Regular or random: a discussion on SPH initial particle distribution
Young, J.; Alcántara, I.; Teixeira-Dias, F.; Ooi, J.; Mill, F.
Smoothed Particle Hydrodynamics (SPH) has been used to model a variety of objects and for a number of applications in engineering and science. These have ranged from astrophysicstoﬂuidandsolidmechanicsproblems. Muchresearchhasbeendedicatedtoforming a better understanding of the SPH method. As a consequence, new numerical techniques have been developed in order to overcome some of its diﬃculties and limitations. Nonetheless, there is still a gap in information concerning the impact of the initial particle distribution on the eﬀectiveness of the SPH method. With this in mind, a review of existing recommendations for SPH initial conﬁgurations has been conducted in this paper. In addition to this, a numerical exampleispresentedwhichisbasedontheclassical2-Dliddrivencavityproblem,whereinthe upperboundaryexertsahorizontalshearforceontheﬂuidinsidethecavity. Thevelocityofthe lid is v = 10−3 m/s and the cavity is square with length l = 1x10−3 m. The ﬂuid was modelled with a density ρ = 1000 kg/m3, a viscosity µ = 10−3 kg/ms) (Re = 1). These parameters were held constant for all consequent comparisons. The number of particles is varied from (20 × 20) to (80 × 80). The initial distribution is modelled in three diﬀerent ways: (i) regular, (ii) pseudo-random (with a 30% random deviation from the regular grid) and (iii) fully random. Theeﬀectivenessofeachinitialparticledistributionisassessedaccordingtotheﬁeldvelocities and horizontal and vertical centreline velocity proﬁles. The impact of the initial particle distribution is highlighted and compared against a reference CFD result, and recommendations and conclusions are drawn for the SPH method.
2020-05-20T14:32:16ZYoung, J.Alcántara, I.Teixeira-Dias, F.Ooi, J.Mill, F.Smoothed Particle Hydrodynamics (SPH) has been used to model a variety of objects and for a number of applications in engineering and science. These have ranged from astrophysicstoﬂuidandsolidmechanicsproblems. Muchresearchhasbeendedicatedtoforming a better understanding of the SPH method. As a consequence, new numerical techniques have been developed in order to overcome some of its diﬃculties and limitations. Nonetheless, there is still a gap in information concerning the impact of the initial particle distribution on the eﬀectiveness of the SPH method. With this in mind, a review of existing recommendations for SPH initial conﬁgurations has been conducted in this paper. In addition to this, a numerical exampleispresentedwhichisbasedontheclassical2-Dliddrivencavityproblem,whereinthe upperboundaryexertsahorizontalshearforceontheﬂuidinsidethecavity. Thevelocityofthe lid is v = 10−3 m/s and the cavity is square with length l = 1x10−3 m. The ﬂuid was modelled with a density ρ = 1000 kg/m3, a viscosity µ = 10−3 kg/ms) (Re = 1). These parameters were held constant for all consequent comparisons. The number of particles is varied from (20 × 20) to (80 × 80). The initial distribution is modelled in three diﬀerent ways: (i) regular, (ii) pseudo-random (with a 30% random deviation from the regular grid) and (iii) fully random. Theeﬀectivenessofeachinitialparticledistributionisassessedaccordingtotheﬁeldvelocities and horizontal and vertical centreline velocity proﬁles. The impact of the initial particle distribution is highlighted and compared against a reference CFD result, and recommendations and conclusions are drawn for the SPH method.Vertical natural modes of the gravel aggregate in the ballasted railway track
http://hdl.handle.net/2117/188296
Vertical natural modes of the gravel aggregate in the ballasted railway track
Aikawa, Akira
This research investigates the natural vibration characteristics of the ballast layer by using field measurement, full-scale experiments and large-scale finite element analysis. The results indicate that the natural frequency of the vertical elastic vibration of the ballast layer is numerically detected at around 310 Hz at which the whole ballast aggregate repeats the vertical expansion and shrinkage elastically, and that the rigid-body natural vibration numerically occurs approximately at 120 Hz at which the mass of the track structure vibrates simultaneously up and down as depending on the stiffness of the ballast layer. The stress acting on an angularity part of the ballast gravel is inferred to be about 1100 times greater than the average stress on the bottom surface of the sleepers.
2020-05-20T14:27:26ZAikawa, AkiraThis research investigates the natural vibration characteristics of the ballast layer by using field measurement, full-scale experiments and large-scale finite element analysis. The results indicate that the natural frequency of the vertical elastic vibration of the ballast layer is numerically detected at around 310 Hz at which the whole ballast aggregate repeats the vertical expansion and shrinkage elastically, and that the rigid-body natural vibration numerically occurs approximately at 120 Hz at which the mass of the track structure vibrates simultaneously up and down as depending on the stiffness of the ballast layer. The stress acting on an angularity part of the ballast gravel is inferred to be about 1100 times greater than the average stress on the bottom surface of the sleepers.On some drawbacks and possible improvements of a lagrangian finite element approach for simulating incompressible flows
http://hdl.handle.net/2117/188294
On some drawbacks and possible improvements of a lagrangian finite element approach for simulating incompressible flows
Cerquaglia, Marco Lucio; Deliege, Geoffrey; Boman, Romain; Papeleux, Luc; Terrapon, Vincent; Ponthot, Jean-Philippe
In this paper a Lagrangian ﬁnite element approach for the simulation of incompressible ﬂows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the deﬁnition of the boundary terms are discussed in detail with a speciﬁc focus on free-surface ﬂows. Additionally, some problems that can arise from the use of such a method are pointed out. Some numerical examples are given and discussed in the last section of the paper.
2020-05-20T14:24:48ZCerquaglia, Marco LucioDeliege, GeoffreyBoman, RomainPapeleux, LucTerrapon, VincentPonthot, Jean-PhilippeIn this paper a Lagrangian ﬁnite element approach for the simulation of incompressible ﬂows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the deﬁnition of the boundary terms are discussed in detail with a speciﬁc focus on free-surface ﬂows. Additionally, some problems that can arise from the use of such a method are pointed out. Some numerical examples are given and discussed in the last section of the paper.Numerical simulation of penetration problems in geotechnical engineering with the particle finite element method (PFEM)
http://hdl.handle.net/2117/188293
Numerical simulation of penetration problems in geotechnical engineering with the particle finite element method (PFEM)
Monforte Vila, Lluís; Carbonell Puigbó, Josep Maria; Gens Solé, Antonio; Arroyo Alvarez de Toledo, Marcos
This paper highlights a computational framework for the numerical analysis of saturated soil-structure interaction problems. The variational equations of linear momentum and mass balance are obtained for the large deformation case. These equations are solved using the Particle Finite Element Method. The paper concludes with a benchmark test and the analysis of a penetration test.
2020-05-20T14:20:25ZMonforte Vila, LluísCarbonell Puigbó, Josep MariaGens Solé, AntonioArroyo Alvarez de Toledo, MarcosThis paper highlights a computational framework for the numerical analysis of saturated soil-structure interaction problems. The variational equations of linear momentum and mass balance are obtained for the large deformation case. These equations are solved using the Particle Finite Element Method. The paper concludes with a benchmark test and the analysis of a penetration test.Numerical modeling of metal cutting processes using the particle finite element method (PFEM) and a physically based plasticity model
http://hdl.handle.net/2117/188290
Numerical modeling of metal cutting processes using the particle finite element method (PFEM) and a physically based plasticity model
Rodríguez, J. M.; Jonsén, P.; Svoboda, A.
Metal cutting is one of the most common metal shaping processes. Specified geometrical and surface properties are obtained by break-up of material and removal by a cutting edge into a chip. The chip formation is associated with large strain, high strain rate and locally high temperature due to adiabatic heating which make the modeling of cutting processes difficult. Furthermore, dissipative plastic and friction work generate high local temperatures. These phenomena together with numerical complications make modeling of metal cutting difficult. Material models, which are crucial in metal cutting simulations, are usually calibrated based on data from material testing. Nevertheless, the magnitude of strain and strain rate involved in metal cutting are several orders higher than those generated from conventional material testing. Therefore, a highly desirable feature is a material model that can be extrapolated outside the calibration range. In this study a physically based plasticity model based on dislocation density and vacancy concentration is used to simulate orthogonal metal cutting of AISI 316L. The material model is implemented into an in-house Particle Finite Element Method software. Numerical simulations are in agreement with experimental results, but also with previous results obtained with the finite element method.
2020-05-20T14:14:45ZRodríguez, J. M.Jonsén, P.Svoboda, A.Metal cutting is one of the most common metal shaping processes. Specified geometrical and surface properties are obtained by break-up of material and removal by a cutting edge into a chip. The chip formation is associated with large strain, high strain rate and locally high temperature due to adiabatic heating which make the modeling of cutting processes difficult. Furthermore, dissipative plastic and friction work generate high local temperatures. These phenomena together with numerical complications make modeling of metal cutting difficult. Material models, which are crucial in metal cutting simulations, are usually calibrated based on data from material testing. Nevertheless, the magnitude of strain and strain rate involved in metal cutting are several orders higher than those generated from conventional material testing. Therefore, a highly desirable feature is a material model that can be extrapolated outside the calibration range. In this study a physically based plasticity model based on dislocation density and vacancy concentration is used to simulate orthogonal metal cutting of AISI 316L. The material model is implemented into an in-house Particle Finite Element Method software. Numerical simulations are in agreement with experimental results, but also with previous results obtained with the finite element method.Vortex particle method for aerodynamic analysis: parallel scalability and efficiency
http://hdl.handle.net/2117/188289
Vortex particle method for aerodynamic analysis: parallel scalability and efficiency
Ibrahim, K.; Morgenthal, G.
This paper presents an analysis of the scalability and eﬃciency of a simulation framework based on the Vortex Particle Method (VPM). The code is applied for the numerical aerodynamic analysis of line-like structures. The numerical code runs on multicore CPU and GPU architectures using OpenCL framework. The focus of this paper is the analysis of the parallel eﬃciency and scalability of the method being applied to an engineering test case, namely the aero-elastic response of a long-span bridge girder. The target is to assess the optimal conﬁguration and the required computer architecture, such that it becomes feasible to eﬃciently utilize the method within the computational resources available for a regular engineering oﬃce. The simulations and the scalability analysis are performed on a regular gaming-type computer.
2020-05-20T14:10:56ZIbrahim, K.Morgenthal, G.This paper presents an analysis of the scalability and eﬃciency of a simulation framework based on the Vortex Particle Method (VPM). The code is applied for the numerical aerodynamic analysis of line-like structures. The numerical code runs on multicore CPU and GPU architectures using OpenCL framework. The focus of this paper is the analysis of the parallel eﬃciency and scalability of the method being applied to an engineering test case, namely the aero-elastic response of a long-span bridge girder. The target is to assess the optimal conﬁguration and the required computer architecture, such that it becomes feasible to eﬃciently utilize the method within the computational resources available for a regular engineering oﬃce. The simulations and the scalability analysis are performed on a regular gaming-type computer.Modeling of elasto-plastic behaviour of granular materials using multi-particle finite element simulations
http://hdl.handle.net/2117/188288
Modeling of elasto-plastic behaviour of granular materials using multi-particle finite element simulations
Abdelmoula, Nouha; Harthong, Barthélémy; Imbault, Didier; Dorémus
The method of multi-particle ﬁnite element involving assemblies of meshed particles interacting through ﬁnite-element contact conditions is adopted to study the plastic ﬂow of a granular material with highly deformable elastic-plastic grains. In particular, it is investigated whether the ﬂow rule postulate applies for such materials. Using a spherical stress probing method, the inﬂuence of incremental stress on plastic strain increment vectors was assessed for numerical samples compacted along two diﬀerent loading paths up to diﬀerent values of relative density. Results show that the numerical samples studied behave reasonnably well according to an associated ﬂow rule, except in the vicinity of the loading point where the inﬂuence of the stress increment proves to be very signiﬁcant. The inﬂuence of relative density and initial loading path is discussed.
2020-05-20T14:08:28ZAbdelmoula, NouhaHarthong, BarthélémyImbault, DidierDorémusThe method of multi-particle ﬁnite element involving assemblies of meshed particles interacting through ﬁnite-element contact conditions is adopted to study the plastic ﬂow of a granular material with highly deformable elastic-plastic grains. In particular, it is investigated whether the ﬂow rule postulate applies for such materials. Using a spherical stress probing method, the inﬂuence of incremental stress on plastic strain increment vectors was assessed for numerical samples compacted along two diﬀerent loading paths up to diﬀerent values of relative density. Results show that the numerical samples studied behave reasonnably well according to an associated ﬂow rule, except in the vicinity of the loading point where the inﬂuence of the stress increment proves to be very signiﬁcant. The inﬂuence of relative density and initial loading path is discussed.A master equation for force distributions in polydisperse frictional particles
http://hdl.handle.net/2117/188287
A master equation for force distributions in polydisperse frictional particles
Saitoh, Kuniyasu; Magnanimo, Vanessa; Luding, Stefan
An incremental evolution equation, i.e. a Master equation in statistical mechanics, is introduced for force distributions in polydisperse frictional particle packings. As basic ingredients of the Master equation, the conditional probability distributions of particle overlaps are determined by molecular dynamics simulations. Interestingly, tails of the distributions become much narrower in the case of frictional particles than frictionless particles, implying that correlations of overlaps are strongly reduced by microscopic friction. Comparing diﬀerent size distributions, we ﬁnd that the tails are wider for the wider distribution.
2020-05-20T14:03:26ZSaitoh, KuniyasuMagnanimo, VanessaLuding, StefanAn incremental evolution equation, i.e. a Master equation in statistical mechanics, is introduced for force distributions in polydisperse frictional particle packings. As basic ingredients of the Master equation, the conditional probability distributions of particle overlaps are determined by molecular dynamics simulations. Interestingly, tails of the distributions become much narrower in the case of frictional particles than frictionless particles, implying that correlations of overlaps are strongly reduced by microscopic friction. Comparing diﬀerent size distributions, we ﬁnd that the tails are wider for the wider distribution.The aerodynamics of a jet of particles in a channel
http://hdl.handle.net/2117/188286
The aerodynamics of a jet of particles in a channel
Logachev, I. N.; Logachev, K. I.; Averkova, O. A.; Uvarov, V. A.; Logachev, A. K.
The main cause for dust discharge is ejection, i.e. formation of directional air flows in a stream of a bulk material due to the dynamic interaction of bombarding particles with air. Discovery of induced air flow occurrence regularities enables both forecasting the level of air pollutions with aerosol emission and choosing the optimum engineering solutions of air containment and dedusting. So far we have studied solid particles flowing in a chute and a jet of loose matter. Both situations represent extreme cases of the more general problem of material flowing through a duct with different distances between flow boundaries and duct walls. Without detriment to generality of the problem we shall consider a flat flow limited by vertical walls.
2020-05-20T13:58:53ZLogachev, I. N.Logachev, K. I.Averkova, O. A.Uvarov, V. A.Logachev, A. K.The main cause for dust discharge is ejection, i.e. formation of directional air flows in a stream of a bulk material due to the dynamic interaction of bombarding particles with air. Discovery of induced air flow occurrence regularities enables both forecasting the level of air pollutions with aerosol emission and choosing the optimum engineering solutions of air containment and dedusting. So far we have studied solid particles flowing in a chute and a jet of loose matter. Both situations represent extreme cases of the more general problem of material flowing through a duct with different distances between flow boundaries and duct walls. Without detriment to generality of the problem we shall consider a flat flow limited by vertical walls.Particle tracking numerical methods for nanoparticle transport in heterogeneous porous media
http://hdl.handle.net/2117/188264
Particle tracking numerical methods for nanoparticle transport in heterogeneous porous media
Papavassiliou, Dimitrios V.; Pham, Ngoc
A single-phase flow, lattice Boltzmann method (LBM) is utilized with a Lagrangian particle tracking (LPT) method for the simulation of flow and transport of nanoparticles in a porous medium. The 3D pore matrix is obtained either as a randomly packed with spheres porous medium or from images of segments of rock (sandstone) through micro-computed tomography (-CT). The particles are assumed to be passive. When the particles collide with the solid matrix, they can either adsorb or continue their motion, based on the assumption that the deposition process is a pseudo-first order process. Furthermore, the solid-fluid interface is assumed to be heterogeneous, so that the simulated nanoparticles can adsorb at different rates at different sites of the interface. Simulations are validated with theoretically expected results, based on macroscopic filtration equations.
2020-05-20T12:10:16ZPapavassiliou, Dimitrios V.Pham, NgocA single-phase flow, lattice Boltzmann method (LBM) is utilized with a Lagrangian particle tracking (LPT) method for the simulation of flow and transport of nanoparticles in a porous medium. The 3D pore matrix is obtained either as a randomly packed with spheres porous medium or from images of segments of rock (sandstone) through micro-computed tomography (-CT). The particles are assumed to be passive. When the particles collide with the solid matrix, they can either adsorb or continue their motion, based on the assumption that the deposition process is a pseudo-first order process. Furthermore, the solid-fluid interface is assumed to be heterogeneous, so that the simulated nanoparticles can adsorb at different rates at different sites of the interface. Simulations are validated with theoretically expected results, based on macroscopic filtration equations.