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Energies
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DEM of Multiphase Flows and Powder Processing
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DEM of Multiphase Flows and Powder Processing

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J: Thermal Management".

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 12397

Special Issue Editor

Prof. Dr. Yutaka Tsuji

E-Mail Website
Guest Editor
Department of Mechanical Engineering, Osaka University, Osaka 565-0871, Japan
Interests: discrete particle simulation; cfd-dem; multiphase flow; gas-solid two-phase flow; pneumatic conveying; measurement of multiphase flow; dynamics of table tennis ball

Special Issue Information

Dear colleagues,

The DEM (discrete element method), which was developed in the 1970s for rock mechanics, has been widely used in many scientific, engineering, and industrial fields. The combination of CFD (computational fluid dynamics) and DEM has further extended its application to various particle-related processes. The particle sizes treated in DEM range from granulate to nanoparticles. Originally, DEM was applied to the dry system in the main, but now its application spreads in the wet system of slurry and colloid. Complicated cases with heat transfer, chemical reaction, and phase change are presented as examples of DEM simulation. Industry interest in DEM and CFD-DEM simulation is growing enormously because all the processing related to powder has become the objects of this simulation. The emergence of several commercial soft wares and free online programs reflects this situation.

The characteristics of phenomena associated with powder and particles are that there are so many influential factors in practical use that accurate prediction of phenomena is not easy in general even today. Examples of such factors include particle shape, sticky properties, electric properties, weather conditions, etc. In addition to those particle properties, the reactor structure complicates particle motion because various mechanical parts such as impellers for mixing, pipes for heat exchange, etc. are inserted in many cases.

Compared with the continuum model, DEM is advantageous in dealing with the effects of these factors. In fact, the effects of several factors are predicted well owing to the achievement of DEM researchers. However, studies of the many effects are still under development. Further, we have to admit the crucial disadvantages of DEM. That is, the computation load is quite heavy in DEM compared to other numerical methods. Hence, the number of particles is limited. To overcome this demerit, something innovative is required.

This Special Issue will focus on all aspects of DEM and CFD-DEM simulation from fundamental research to applications. We encourage the development of algorisms for efficient calculation, unprecedented application, and utilization of AI.

Prof. Dr. Yutaka Tsuji
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • discrete element method
  • discrete particle simulation
  • computational fluid dynamics
  • numerical analysis
  • multiphase flow
  • powder processing
  • DEM
  • CFD-DEM

Published Papers (5 papers)

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Research

12 pages, 2205 KiB  
Article
A Model to Improve Granular Temperature in CFD-DEM Simulations
by Yaxiong Yu, Li Zhao, Yu Li and Qiang Zhou
Energies 2020, 13(18), 4730; https://doi.org/10.3390/en13184730 - 11 Sep 2020
Cited by 7 | Viewed by 2210
Abstract
CFD-DEM (computational fluid dynamic-discrete element method) is a promising approach for simulating fluid–solid flows in fluidized beds. This approach generally under-predicts the granular temperature due to the use of drag models for the average drag force. This work develops a simple model to [...] Read more.
CFD-DEM (computational fluid dynamic-discrete element method) is a promising approach for simulating fluid–solid flows in fluidized beds. This approach generally under-predicts the granular temperature due to the use of drag models for the average drag force. This work develops a simple model to improve the granular temperature through increasing the drag force fluctuations on the particles. The increased drag force fluctuations are designed to match those obtained from PR-DNSs (particle-resolved direct numerical simulations). The impacts of the present model on the granular temperatures are demonstrated by posteriori tests. The posteriori tests of tri-periodic gas–solid flows show that simulations with the present model can obtain transient as well as steady-state granular temperature correctly. Moreover, the posteriori tests of fluidized beds indicated that the present model could significantly improve the granular temperature for the homogenous or slightly inhomogeneous systems, while it showed negligible improvement on the granular temperature for the significantly inhomogeneous systems. Full article
(This article belongs to the Special Issue DEM of Multiphase Flows and Powder Processing)
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19 pages, 6230 KiB  
Article
Particle-Scale Simulation of Solid Mixing Characteristics of Binary Particles in a Bubbling Fluidized Bed
by Junjie Lin, Kun Luo, Shuai Wang, Liyan Sun and Jianren Fan
Energies 2020, 13(17), 4442; https://doi.org/10.3390/en13174442 - 27 Aug 2020
Cited by 11 | Viewed by 2218
Abstract
The behavior of solid mixing dynamic is of profound significance to the heat transfer and reaction efficiencies in energy engineering. In the current study, the solid mixing characteristics of binary particles in the bubbling fluidized bed are further revealed at particle-scale. Specifically, the [...] Read more.
The behavior of solid mixing dynamic is of profound significance to the heat transfer and reaction efficiencies in energy engineering. In the current study, the solid mixing characteristics of binary particles in the bubbling fluidized bed are further revealed at particle-scale. Specifically, the influences of gas superficial velocity, Sauter mean diameter (SMD) in the system and the range distribution of particle sizes on the performance of mixing index are quantitatively explored using a computational fluid dynamics-discrete element method (CFD-DEM) coupling model. The competition between solid segregation and the mixing of binary particles is deeply analyzed. There is a critical superficial velocity that maximizes the mixing index of the binary mixture in the bubbling fluidized bed. Solid mixing performs more aggressive when below the critical velocity, otherwise solid segregation overtakes mixing when above this critical velocity. Moreover, superficial velocity is a major factor affecting the mixing efficiency in the binary bubbling fluidized bed. Additionally, the mixing behavior is enhanced with the decrease of SMD while it is deteriorated in the binary system with a wide range of particle size distribution. Therefore, it is highly recommended to perform a binary particle system with smaller SMD and closer particle size distribution for the purpose of enhancing the mixing behavior. The significant understanding of mixing characteristics is expected to provide valuable references for the design, operation, and scale-up of binary bubbling fluidized bed. Full article
(This article belongs to the Special Issue DEM of Multiphase Flows and Powder Processing)
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Graphical abstract

10 pages, 4994 KiB  
Article
Analysis of the Effect of Ventilation Bars on the Packing Structure of Sinter Bed by DEM Simulation
by Shingo Ishihara, Kizuku Kushimoto and Junya Kano
Energies 2020, 13(15), 3836; https://doi.org/10.3390/en13153836 - 27 Jul 2020
Cited by 3 | Viewed by 1897
Abstract
The effect of ventilation bars on the porosity of a sinter bed charged on a sinter machine was investigated. The behavior of the sinter feed was calculated by discrete element method (DEM) simulation. By taking into account the adhesion force, the sinter feed [...] Read more.
The effect of ventilation bars on the porosity of a sinter bed charged on a sinter machine was investigated. The behavior of the sinter feed was calculated by discrete element method (DEM) simulation. By taking into account the adhesion force, the sinter feed in the wet state was represented and the simulation parameters were determined to reproduce the experimental values of the angle of repose. The porosity of the sinter bed was calculated, and the mechanism of the formation of the packing structure and the cause of the distribution of porosity in each region were clarified. As a result, it is shown that in the case of shear flow, the higher the powder pressure during flow, the higher the porosity. Full article
(This article belongs to the Special Issue DEM of Multiphase Flows and Powder Processing)
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17 pages, 5795 KiB  
Article
Mechanical Performances of Typical Robot Feet Intruding into Sands
by Dianlei Han, Rui Zhang, Hua Zhang, Zhenyu Hu and Jianqiao Li
Energies 2020, 13(8), 1867; https://doi.org/10.3390/en13081867 - 11 Apr 2020
Cited by 6 | Viewed by 2246
Abstract
Four kinds of feet with typical structures, referred to as the hemispherical foot, the semicylindrical foot, the rectangular foot and the circular foot, respectively, were designed and manufactured to study the foot–terrain interaction mechanics for legged robots. Three kinds of quartz sand were [...] Read more.
Four kinds of feet with typical structures, referred to as the hemispherical foot, the semicylindrical foot, the rectangular foot and the circular foot, respectively, were designed and manufactured to study the foot–terrain interaction mechanics for legged robots. Three kinds of quartz sand were selected to study how particle size, shape and compactness affected the physical properties of the substrate and the intrusion performance of mechanical feet. The media with smaller particle sizes had higher bulk densities and lower angles of stability, but no obvious rule was found for particle shapes of quartz sand with different sizes. The intrusion resistive forces and pressures of the hemispherical foot on these three kinds of quartz sand were all less compared with the other three mechanical feet. The particle disturbance areas and motion trends were compared under these four kinds of mechanical feet using discrete element method simulations. The intrusion resistive forces of these mechanical feet first increased and then decreased with the increasing particle sizes of the quartz sand. Moreover, the intrusion resistive forces of these mechanical feet on spherical particles were smaller compared with irregular particles. The corresponding resistive forces of the mechanical feet were characterized based on the compactness of the quartz sand. According to the intrusion test data, the classic pressure–sinkage model was modified, and the relationships between intrusion resistive force and mechanical foot depth were obtained. Full article
(This article belongs to the Special Issue DEM of Multiphase Flows and Powder Processing)
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Graphical abstract

25 pages, 9228 KiB  
Article
Discrete Element Method Investigation of Binary Granular Flows with Different Particle Shapes
by Yi Liu, Zhaosheng Yu, Jiecheng Yang, Carl Wassgren, Jennifer Sinclair Curtis and Yu Guo
Energies 2020, 13(7), 1841; https://doi.org/10.3390/en13071841 - 10 Apr 2020
Cited by 10 | Viewed by 3269
Abstract
The effects of particle shape differences on binary mixture shear flows are investigated using the Discrete Element Method (DEM). The binary mixtures consist of frictionless rods and disks, which have the same volume but significantly different shapes. In the shear flows, stacking structures [...] Read more.
The effects of particle shape differences on binary mixture shear flows are investigated using the Discrete Element Method (DEM). The binary mixtures consist of frictionless rods and disks, which have the same volume but significantly different shapes. In the shear flows, stacking structures of rods and disks are formed. The effects of the composition of the mixture on the stacking are examined. It is found that the number fraction of stacking particles is smaller for the mixtures than for the monodisperse rods and disks. For binary mixtures with small particle shape differences, the mixture stresses are bounded by the stresses of the two corresponding monodisperse systems. However, for binary mixtures with large particle shape differences, the stresses of the mixtures can be larger than the stresses of the monodisperse systems at large solid volume fractions because larger differences in particle shape cause geometrical interference in packing, leading to stronger particle–particle interactions in the flow. The stresses in dense binary mixtures are found to be exponential functions of the order parameter, which is a measure of particle alignment. Based on the simulation results, an empirical expression for the bulk friction coefficient (ratio of the shear stress to normal stress) for dense binary flows is proposed by accounting for the effects of particle alignment and solid volume fraction. Full article
(This article belongs to the Special Issue DEM of Multiphase Flows and Powder Processing)
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