Numerical analysis of wet separation of particles by density differences

Wet particle separation is widely used in mineral processing and plastic recycling to separate mixtures of particulate materials into further usable fractions due to density differences. This work presents efforts aiming to numerically analyze the wet separation of particles with different densities. In the current study the discrete element method (DEM) is used for the solid phase while the smoothed particle hydrodynamics (SPH) is used for modeling of the liquid phase. The two phases are coupled by the use of a volume averaging technique. In the current study, simulations of spherical particle separation were performed. In these simulations, a set of generated particles with two different densities is dropped into a rectangular container filled with liquid. The results of simulations with two different mixtures of particles demonstrated how separation depends on the densities of particles.Comment: This manuscript was accepted for the publication in the conference proceedings of ICNAAM 2016 conferenc

Investigation of rice grain flow by multi-sphere particle model with rolling resistance

A multi-sphere (MS) model combined with rolling friction was considered for modelling elongated particles of irregular shape. The performance of the model was investigated by numerical simulations of the rice grain flow. A set of 5000 poly-dispersed milled rice grains were selected for the investigation purposes. They were characterised by a constant aspect ratio 3.5, while their maximum size was ranging from 6.4 to 7.3 mm. Filling and discharge flow as well as piling were simulated numerically with and without rolling resistance of particles. Simulation results were validated on the basis of experimental results. Good agreement of numerical and experimental results in terms of the discharge time and repose angle of the pile was reached simultaneously, when rolling resistance was introduced

Investigation of adequacy of multi-sphere approximation of elliptical particles for DEM simulations

Adequacy of approximation of ellipsoidal particles composed of a set of sub-spheres for numerical Discrete Element Method (DEM) simulations is examined. The algorithm of adaptive hierarchical multi-sphere (MS) model is suggested for composing elliptical particles. Numerical simulation of the piling problem is used as a test problem for evaluating the adequacy of MS model approximation in comparison to the model of smooth ellipses for multiparticle system. The accuracy of MS approximation with the increasing number of sub-spheres is examined in detail by comparison of macroscopic and microscopic parameters of granular dynamics. It was determined that the data on macroscopic parameters yielded by the MS model tend to converge to those of the smooth ellipsoid with the increasing number of the constituent sub-spheres, and the MS model approximates the smooth perfect ellipsoid with a reasonable number of sub-spheres within the limits of the appropriate tolerance. It can be concluded that a multi-sphere model remains a realistic and relatively simple particle model applicable to DEM simulations of the behaviour of the real smooth and rough elliptically shaped particles

Sensitivity of dynamic behaviour of the FE model: Case study for the ignalina NPP reactor building

The 3D thin‐walled finite element model of Ignalina NPP Unit 2 reactor building was developed aimed at the evaluation of the global dynamic behaviour with a focus on the seismic response. The model comprises description of the monolithic structures, while prefabricated frame structures are ignored and replaced by external masses. Sensitivity study of the selected dynamic characteristics of the model with respect to data uncertainties is considered. Uncertainty of the model is considered in terms of masses of removed structures and wall stiffness. Seismic input is represented by the site specific free‐field ground response acceleration spectra. The sensitivity study concerns variations of frequencies and acceleration of in‐structure horizontal response spectra at specified points. Maximal bending moments are also considered. It was obtained that the reactor level is not sensitive to the uncertainties considered, while discernable sensitivity was detected at the top level of the structure. Santrauka Pateikta Ignalinos atominės elektrinės pastato erdvinio baigtinių elementų dinaminio modelio kūrimo koncepcija, išnagrinėtas šio modelio jautrumas keičiamoms masėms ir sienų standumui. Parodyta, kaip šie keičiami dydžiai turi įtaką dažniams, horizontaliems tam tikrų nagrinėjamų taškų atsako spektrams, lenkimo momentų persiskirstymui ir jų didžiui. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: Ignalinos AE, baigtinių elementų modelis, savųjų dažnių ir seisminė analizė, plyno lauko spektras, atsako spektras

Discrete element modelling of complex axisymmetrical particle flow

In the paper the simulation of complex axisymmetrical particle flow by Discrete Element Method is considered. Complex particles are constructed from a number of spheres which centres are located on the axis of symmetry. The relationships which describe these particles are presented and implemented into the code. The discharge rate analysis of the plane-wedged hopper is performed

Moving locally predefined remeshing for deep cone penetration FE analysis

The paper considers moving locally predefined (MLP finite element remeshing technique for deep penetration of the rigid cone into homogeneous and porous medium. Remeshing presents a computation tool implemented in the form of postprocessor type software compatible with standard FEM code. It involves a transfer operation combining both the moving least square method based on stress patch recovery and the interpolation method for transfer of state variables. [...]

Numerical stress analysis of granular material

From the experimental point of view, it is very difficult to obtain accurate stress measurements within the bulk of granular material. The numerical stress analysis based on the forces acting on the discrete particle was per-formed. Verification of the obtained results and their com-patibility with well-known continuum-based indications were demonstrated

Investigation of the geometric rolling resistance in DEM simulations of piling

Since the publication of the work by Cundall and Strack in 1979, the discrete element method (DEM) has become the most popular technique used to investigate granular assemblies by numerical simulations. The DEM was initially aimed at simulating spherical particles, however, the diversity of real particle shapes required new more sophisticated particle models. In the present paper the rolling resistance of individual particles resulting from particle geometry is investigated. It enables to consider non-sphericity of real non-round particles described by spherical models. This approach is applied to simulate the formation of 3D pile. Piling and evaluation of the repose angle of the pile is frequently explored to characterize particle properties by dynamic experiments. The pile is formed via hopper discharge, while the repose angle is defined from the pile slope

Compacting of particles for biaxial compression test by the discrete element method

Numerical simulation of the compacting of particles for the biaxial compression test using the discrete element method is presented. Compacting is considered as the first independent step required for a proper simulation of the entire compression process. In terms of the continuum approach, compacting is regarded as generation of the initial conditions. Three different compacting scenarios with differently manipulated loading history on the boundaries, namely, compacting by using the moving rigid walls, by the static pressure using flexible membranes as well as combining the above two methods are considered. Discrete element methodology and basic relations, as well as formulation of the compacting problem and computational aspects of compacting are presented in detail. Each of the scenarios is illustrated by the numerical results. It has been found that the combined compacting scenario yields the required initial conditions exhibiting the best physically adjustable state of particles. Dalelių tankinimas diskretinių elementų metodu dviaÅ¡iam kompresijos bandymui atlikti Santrauka Å iame straipsnyje pateiktas skaitinis dalelių tankinimo modeliavimas diskretinių elementų metodu dviaÅ¡iam kompresijos bandymui atlikti. Tankinimas nagrinÄ—jamas kaip pirmasis nepriklausomas veiksmas, reikalingas, kad bÅ«tų galima atlikti viso kompresijos bandymo modeliavimÄ…. Kontinuumo teorijos požiÅ«riu sutankinimas yra pradinių sÄ…lygų generavimas. NagrinÄ—jami trys skirtingi tankinimo pavyzdžiai keiÄiant apkrovÄ…. Diskretinių elementų metodologija ir pagrindiniai sÄ…ryÅ¡iai, taip pat tankinimo problemos formulavimas ir skaiÄiavimo aspektai Äia detaliai iÅ¡dÄ—styti. KiekvienÄ… pavyzdį iliustruoja skaitiniai rezultatai. Tyrimo metu nustatyta, kad, naudojant miÅ¡rųjį tankinimÄ…, gaunamos reikiamos pradinÄ—s sÄ…lygos. Raktiniai žodžiai: diskretinių elementų metodas, klampiai tampri granuliuotoji terpÄ—, dviaÅ¡is bandymas, dalelių tankinimas. First Published Online: 14 Oct 201