Axial segregation of a binary mixture in a rotating tumbler with non-spherical particles: Experiments and DEM model validation

2017 ◽  
Vol 306 ◽  
pp. 120-129 ◽  
Author(s):  
Riccardo Maione ◽  
Sébastien Kiesgen De Richter ◽  
Guillain Mauviel ◽  
Gabriel Wild
Keyword(s):  
Binary Mixture ◽  
Model Validation ◽  
Spherical Particles ◽  
Axial Segregation ◽  
Rotating Tumbler ◽  
Dem Model

scholarly journals Modelling bacterial twitching in fluid flows: a CFD-DEM approach

2019 ◽  
Author(s):  
Pahala Gedara Jayathilake ◽  
Bowen Li ◽  
Paolo Zuliani ◽  
Tom Curtis ◽  
Jinju Chen
Keyword(s):  
Fluid Flow ◽  
Shear Flows ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Spherical Particles ◽  
Twitching Motility ◽  
Type Iv ◽  
Computational Fluid Dynamics Cfd ◽  
Dem Model ◽  
Modelling Approach

Bacterial habitats are often associated with fluid flow environments. There is a lack of models of the twitching motility of bacteria in shear flows. In this work, a three-dimensional modelling approach of Computational Fluid Dynamics (CFD) coupled with the Discrete Element Method (DEM) is proposed to study bacterial twitching on flat and groove surfaces under shear flow conditions. Rod-shaped bacteria are modelled as groups of spherical particles and Type IV pili attached to bacteria are modelled as dynamic springs which can elongate, retract, attach and detach. The CFD-DEM model of rod-shape bacteria is validated against orbiting of immotile bacteria in shear flows. The effects of fluid flow rate and surface topography on twitching motility are studied. The model can successfully predict upstream twitching motility of rod-shaped bacteria in shear flows. Our model can predict that there would be an optimal range of wall shear stress in which bacterial upstream twitching is most efficient. The results also indicate that when bacteria twitch on groove surfaces, they are likely to accumulate around the downstream side of the groove walls.

DEM investigation of granular flow and binary mixture segregation in a rotating tumbler: Influence of particle shape and internal baffles

2015 ◽  
Vol 286 ◽  
pp. 732-739 ◽  
Author(s):  
Riccardo Maione ◽  
Sébastien Kiesgen De Richter ◽  
Guillain Mauviel ◽  
Gabriel Wild
Keyword(s):  
Binary Mixture ◽  
Granular Flow ◽  
Particle Shape ◽  
Rotating Tumbler

scholarly journals CFD-DEM Simulation of Fluidization of Polyhedral Particles in a Fluidized Bed

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4939
Author(s):  
Zihan Liu ◽  
Huaqing Ma ◽  
Yongzhi Zhao
Keyword(s):  
Fluidized Bed ◽  
Chemical Engineering ◽  
Spherical Particles ◽  
Gas Velocity ◽  
Reasonable Accuracy ◽  
Dem Simulation ◽  
Polyhedral Particles ◽  
Common Process ◽  
Dem Model

Fluidization of non-spherical particles is a common process in energy industries and chemical engineering. Understanding the fluidization of non-spherical particles is important to guide relevant processes. There already have been numerous studies which investigate the behaviors of different non-spherical particles during fluidization, but the investigations of the fluidization of polyhedral particles do not receive much attention. In this study, the investigation of the fluidization of polyhedral particles described by the polyhedron approach is conducted with a numerical CFD-DEM method. Experiments of the fluidization of three kinds of polyhedral particles are conducted under the same condition with corresponding simulations to validate the accuracy of our CFD-DEM model. The results indicate that our CFD-DEM model with the polyhedron approach can predict the behaviors of polyhedral particles with reasonable accuracy. Fluidization behaviors of different polyhedral particles are also investigated in this study. Compared to spherical particles, the motion of polyhedral particles is stronger, and mixing degree is higher under the same fluidization gas velocity.

Particle size segregation in inclined chute flow of dry cohesionless granular solids

1988 ◽  
Vol 189 ◽  
pp. 311-335 ◽  
Author(s):  
S. B. Savage ◽  
C. K. K. Lun
Keyword(s):  
Binary Mixture ◽  
Fine Particles ◽  
Physical Nature ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Contact Forces ◽  
Spherical Particles ◽  
Concentration Profiles ◽  
Size Segregation ◽  
Void Space

If granular materials comprising particles of identical material but different sizes are sheared in the presence of a gravitational field, the particles are segregated according to size. The small particles fall to the bottom and the larger ones drift to the top of the sheared layer. In an attempt to isolate and study some of the essential segregation mechanisms, the paper considers a simplified problem involving the steady two-dimensional flow of a binary mixture of small and large spherical particles flowing down a roughened inclined chute. The flow is assumed to take place in layers that are in motion relative to one another as a result of the mean shear. For relatively slow flows, it is proposed that there are two main mechanisms responsible for the transfer of particles between layers. The first mechanism, termed the ‘random fluctuating sieve’, is a gravity-induced, size-dependent, void-filling mechanism. The probability of capture of a particle in one layer by a randomly generated void space in the underlying layer is calculated as a function of the relative motion of the two layers. The second, termed the ‘squeeze expulsion’ mechanism, is due to imbalances in contact forces on an individual particle which squeeze it out of its own layer into an adjacent one. It is assumed that this mechanism is not size preferential and that there is no inherent preferential direction for the layer transfer. This second physical mechanism in particular was proposed on the basis of observations of video recordings that were played back at slow speed. Since the magnitude of its contribution is determined by the satisfaction of overall mass conservation, the exact physical nature of the mechanism is of less importance. By combining these two proposed mechanisms the net percolation velocity of each species is obtained. The mass conservation equation for fines is solved by the method of characteristics to obtain the development of concentration profiles with downstream distance. Although the theory involves a number of empirical constants, their magnitude can be estimated with a fair degree of accuracy. A solution for the limiting case of dilute concentration of fine particles and a more general solution for arbitrary concentrations are presented. The analyses are compared with experiments which measured the development of concentration profiles during the flow of a binary mixture of coarse and fine particles down a roughened inclined chute. Reasonable agreement is found between the measured and predicted concentration profiles and the distance required for the complete separation of fine from coarse particles.

Modeling Non-Spherical Particulate Systems in the DEM Framework

2020 ◽  
Author(s):  
Vivek Srinivasan ◽  
Danesh Tafti
Keyword(s):  
Computational Cost ◽  
Spherical Particles ◽  
Flow Solver ◽  
Factors Affecting ◽  
Practical Applications ◽  
Dense Fluid ◽  
Conservation Of Momentum ◽  
Major Factors ◽  
Dem Model ◽  
Particulate Systems

Abstract Particulate systems in practical applications have mostly been represented using spherical shapes, even though the majority of particles in archetypal fluid-solid systems are non-spherical. Modeling dense fluid-particulate systems using non-spherical particles involves increased complexity, with computational cost manifesting as the biggest bottleneck. In this research, a novel Discrete Element Method (DEM) model that incorporates geometry definition, collision detection, and post-collision kinematics has been developed to accurately simulate non-spherical particulate systems. Superellipsoids, which account for 80% of particles commonly found in nature, are used to represent non-spherical shapes. Collisions between these particles are processed using a hierarchical detection method. An event-driven model and a time-driven model have been employed in the current framework to resolve collisions. The collision model’s influence on non-spherical particle dynamics is verified by observing the conservation of momentum and total kinetic energy. Furthermore, the non-spherical DEM model is coupled with an in-house fluid flow solver (GenIDLEST). The combined CFDDEM model results are validated by comparing to experimental measurements in a fluidized bed. The parallel scalability of the non-spherical DEM model is evaluated in terms of its efficiency and speedup. Major factors affecting wall clock time of simulations are analyzed and an estimate of the model’s dependency on these factors is given.

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