Large-scale CFD–DEM simulations of fluidized granular systems

Jajčević, Dalibor; Siegmann, Eva; Radeke, Charles; Khinast, Johannes G.

doi:10.1016/j.ces.2013.05.014

Cited by 204 publications

(82 citation statements)

References 35 publications

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“…We refrai using this term, as it may be misleading for pressures that are smaller th of subglacial materials in a few select scenarios, e.g., when pore-water flow due to porosity change in early stages of shear deformation is limited by low hydraulic diffusivities (e.g., Iverson, 2010). The mechanics of coupled granularfluid mixtures have previously been numerically investigated for studies of fluidized beds (e.g., Anderson and Jackson, 1967;Gidaspow et al, 1992;Hoomans et al, 1996;Xu and Yu, 1997;McNamara et al, 2000;Feng and Yu, 2004;Jajcevic et al, 2013), the stability of inclined, fluid-immersed granular materials (e.g., Topin et al, 2011;Mutabaruka et al, 2014), mechanics during confined deformation (e.g., Goren et al, 2011;Catalano et al, 2014), debris flow (e.g., Hutter et al, 1994;Mangeney et al, 2007;Goren et al, 2011), and for the design of industrial components, e.g., hydrocyclones (e.g., Wang et al, 2007;Zhou et al, 2010), or silos and hoppers (Kloss et al, 2012). In this study, we explore the interaction between the fluid and granular phases in water-saturated consolidated particle assemblages undergoing slow shear deformation.…”

Section: The Fluid Modelmentioning

confidence: 99%

A new methodology to simulate subglacial deformation of water-saturated granular material

et al. 2015

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Abstract. The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grainfluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions.Our computational experiments support the findings of previous studies where the rheology of a slowly deforming water-saturated granular bed in the steady state generally conforms to the rate-independent plastic rheology. Before this so-called critical state, deformation is in many cases accompanied by volumetric changes as grain rearrangement in active shear zones changes the local porosity. For previously consolidated beds porosity increases can cause local pore-pressure decline, dependent on till permeability and shear rate. We observe that the pore-water pressure reduction strengthens inter-granular contacts, which results in increased shear strength of the granular material. In contrast, weakening takes place when shear deformation causes consolidation of dilated sediments or during rapid fabric development. Both processes of strengthening and weakening depend inversely on the sediment permeability and are transient phenomena tied to the porosity changes during the early stages of shear.We find that the transient strengthening and weakening in turn influences the distribution of shear strain in the granular bed. Dilatant strengthening has the ability to distribute strain during early deformation to large depths, if sediment dilatancy causes the water pressure at the ice-bed interface to decline. Oppositely, if the ice-bed interface is hydrologically stable the strengthening process is minimal and instead causes shallow deformation. The depth of deformation in subglacial beds thus seems to be governed by not only local grain and pore-water feedbacks but also larger-scale hydrological properties at the ice base.

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Section: The Fluid Modelmentioning

confidence: 99%

A new methodology to simulate subglacial deformation of water-saturated granular material

et al. 2015

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“…For many particle coating processes in pharmaceutical development, the systems often have a batch size ranging from a few grams to a few hundred grams, which corresponds to from tens of thousands to a few million particles. Nowadays, simulating tens of thousands particles can be done at a reasonable computational cost, while modeling systems with a few million particles is challenging, though still feasible (Jajcevic D. et al, 2013). Hence, DEM-CFD modeling offers a great opportunity to assist process and product development.…”

Section: Introductionmentioning

confidence: 99%

Effect of Drag Models on Residence Time Distributions of Particles in a Wurster Fluidized Bed: a DEM-CFD Study

Remmelgas

Wachem

et al. 2016

KONA

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Fluidized bed coating has been used to coat pellets or tablets with functional substances for a number of purposes. In this coating process, particle wetting, drying and film formation are coupled to particle motion. It is therefore of interest to study particle motion in such fluidized beds and to use the results to develop a model for predicting the quality of the final product. In this paper, we present results from DEM-CFD simulations, i.e. discrete element method and computational fluid dynamics simulations of particle motion in a laboratory-scale Wurster fluidized bed that was also employed in positron emission particle tracking (PEPT) experiments. As the drag force is the dominant interaction between the gas flow and the particle motion in this type of fluidized bed, the effect of drag models on the particle motion is investigated. More specifically, the particle velocity and residence time distributions of particles in different regions calculated from five different drag models are presented. It is found that the Gidaspow and Tang drag models predict both particle cycle and residence times well. The HKL and Beetstra drag models somewhat overestimate the particle velocity in the Wurster tube and therefore predict a reduced number of recirculations and a significantly shorter cycle time.

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“…This combined method gives us a possibility to generate detailed grain scale information (to describe the acting forces and trajectory of individual grains) [14]. Many scientific works demonstrated that this combined approach is effective to examine the flow and heat transfer in fluidized systems [13][14][15]. But every mathematical model should be proved by experiments.…”

Section: Introductionmentioning

confidence: 99%

“…If we want to describe the processes such as mass, heat transfer in pseudofluidized layer and investigate coupled gas-particle flows, it is better to combine computation fluid dynamics models with discrete element method models [14]. This combined method gives us a possibility to generate detailed grain scale information (to describe the acting forces and trajectory of individual grains) [14]. Many scientific works demonstrated that this combined approach is effective to examine the flow and heat transfer in fluidized systems [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

“…This problem can be solved with the discrete element method [13; 14]. If we want to describe the processes such as mass, heat transfer in pseudofluidized layer and investigate coupled gas-particle flows, it is better to combine computation fluid dynamics models with discrete element method models [14]. This combined method gives us a possibility to generate detailed grain scale information (to describe the acting forces and trajectory of individual grains) [14].…”

Section: Introductionmentioning

confidence: 99%

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Results of laboratory studies of grain drying in fluidized bed dryer

Цивенкова

Nezdvetskaya

Yarosh

et al. 2018

Engineering for Rural Development

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Abstract. A paper presents mathematical modelling and experimental results of grain drying in a dryer with pseudofluidized bed with intermittent drying media supply, working on producer gas. A system of four differential equations that interconnects the grain moisture content and temperature and drying media temperature humidity are presented. Straw and producer gas consumption for grain drying is presented. A multifactor experiment is done, where the drying media temperature, number of sections and sections blowing time are variable factors. Response surfaces are built on these data. Experimental results let us define the optimal calm period to the blow period ratio and drying media temperature that provide the highest grain moisture evaporation tempo. The obtained measurement results are in high correlation with the calculations. It illustrates that using gasifier technologies to supply grain dryers is expedient and provides high indexes of economical, energetic and ecological effectiveness, when using straw with the moisture content range of 10-30 %. Using this dryer lowers specific expenses on after harvesting post processing up to 30 %.Keywords: fluidized bed, grain drying, gasifier technologies. IntroductionIn Ukraine existing drying modes in installations with periodical and continuous action do not provide substantial during quality and correspondent energy expenditures. The existing dryers have a low coefficient of productivity (CoP) and high specific material consumption [1].As an alternative for convectional type dryers there are dryers with pseudofluidized bed [2]. Moist product is dried in the pseudofluidized layer that is created by heated drying media provided through the distribution system maintaining a "boiling" layer in the drying chamber [3][4][5]. Herewith created mode mixes the product effectively that raises the heat transfer coefficient, raising the whole product volume drying effectiveness [4]. While grain is moving in the "boiling" layer through the dryer sections, the used drying media is evacuated through the system of filters and cyclones [2; 6; 7]. For companies that have a surplus of straw, to provide production self-sufficiency and high indexes of ecological and energy efficiency it is expedient to equip dryers with gasifiers [8; 9].Besides pros such dryers have some disadvantages. Separate grains, because of mixing, spend unequal time in the layer. As a result the grain mass can be processed unequally, that is not good especially for sowing grain. Using the gasifier as an energy supply for the dryer makes the situation even more complicated. Thus, there are sufficient achievements in the area of gasifying, especially agricultural raw material and its mixtures [10], however, there is still a problem of coordination between the thermo-technical modes of the gasifier and the dryer operation [9; 11].There are quite enough scientific investigations describing the drying process in the pseudofluidized layer [3; 5; 12], although not all of them represent modelling of drying grain materi...

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Large-scale CFD–DEM simulations of fluidized granular systems

Cited by 204 publications

References 35 publications

A new methodology to simulate subglacial deformation of water-saturated granular material

A new methodology to simulate subglacial deformation of water-saturated granular material

Effect of Drag Models on Residence Time Distributions of Particles in a Wurster Fluidized Bed: a DEM-CFD Study

Results of laboratory studies of grain drying in fluidized bed dryer

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