Large-scale discrete element modeling in a fluidized bed

Fluidized beds with multiple jets have widespread industrial applications. They are used to aid in proper mixing of coal or biomass in the bed, which in turn increases the combustion and heat transfer. The objective of this paper is to investigate the jet interactions and hydrodynamics of a fluidized bed with multiple jets. Discrete Element Modeling coupled with a CFD code GenIDLEST has been used to numerically simulate 9 jets. The results are compared with published experiments. Mono dispersed particles of size 550 microns are used with 1.4 times the minimum fluidization for the particles. Two dimensional computations have been performed. The solid fraction at different heights from the jetting bed is compared with the experiments along with the solid circulation at the grid zone or the jetting zone. Average solid fraction across the cross-section of the bed is plotted along the height and compared with the experiments to estimate the bed expansion due to fluidization. Comparison of time averaged jet heights with the experiments is also shown. Discrepancies between the experiments and simulations are discussed in the context of the dimensionality of the simulations. The time averaged solid fraction at different heights from the distributor plate match well with the experimental results except near the walls. A slight over prediction of solid fraction values is obtained near the walls from the simulations. The average solid fraction along the height of the bed is in good agreement with the experiments, showing similar trends in bed expansion for both the experiments and simulations. The results obtained from DEM computations serve as validation for the experiments and help us understand the complex jet interaction and solid circulation patterns in a multiple jet fluidized bed system.

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Discussion of “Micromechanics-Based Investigation of Fouled Ballast Using Large-Scale Triaxial Tests and Discrete Element Modeling” by Ngoc Trung Ngo, Buddhima Indraratna, and Cholachat Rujikiatkamjorn

Journal of Geotechnical and Geoenvironmental Engineering ◽

10.1061/(asce)gt.1943-5606.0001766 ◽

2017 ◽

Vol 143 (9) ◽

pp. 07017026

Author(s):

Vishnu Diyaljee

Keyword(s):

Large Scale ◽

Discrete Element ◽

Triaxial Tests ◽

Discrete Element Modeling ◽

Element Modeling ◽

Fouled Ballast

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An Energy-Based Discrete Element Modeling Method Coupled with Time-Series Analysis for Investigating Deformations and Failures of Jointed Rock Slopes

Applied Sciences ◽

10.3390/app11125447 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5447

Author(s):

Xiaona Zhang ◽

Gang Mei ◽

Ning Xi ◽

Ziyang Liu ◽

Ruoshen Lin

Keyword(s):

Time Series ◽

Iterative Process ◽

Discrete Element ◽

Jointed Rock ◽

Modeling Method ◽

Discrete Element Modeling ◽

Rock Slopes ◽

Sliding Surface ◽

Element Modeling ◽

Displacement Based

The discrete element method (DEM) can be effectively used in investigations of the deformations and failures of jointed rock slopes. However, when to appropriately terminate the DEM iterative process is not clear. Recently, a displacement-based discrete element modeling method for jointed rock slopes was proposed to determine when the DEM iterative process is terminated, and it considers displacements that come from rock blocks located near the potential sliding surface that needs to be determined before the DEM modeling. In this paper, an energy-based discrete element modeling method combined with time-series analysis is proposed to investigate the deformations and failures of jointed rock slopes. The proposed method defines an energy-based criterion to determine when to terminate the DEM iterative process in analyzing the deformations and failures of jointed rock slopes. The novelty of the proposed energy-based method is that, it is more applicable than the displacement-based method because it does not need to determine the position of the potential sliding surface before DEM modeling. The proposed energy-based method is a generalized form of the displacement-based discrete element modeling method, and the proposed method considers not only the displacement of each block but also the weight of each block. Moreover, the computational cost of the proposed method is approximately the same as that of the displacement-based discrete element modeling method. To validate that the proposed energy-based method is effective, the proposed method is used to analyze a simple jointed rock slope; the result is compared to that achieved by using the displacement-based method, and the comparative results are basically consistent. The proposed energy-based method can be commonly used to analyze the deformations and failures of general rock slopes where it is difficult to determine the obvious potential sliding surface.

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