Discrete Element Model Simulations Research Articles

Analysis and Evaluation of Influencing Factors on Uniform Sowing of Wheat with Wide Seed Belt after Sowing and Soil Throwing Device

The uneven sowing of wheat on ground covered with rice straw in the rice–wheat rotation area in the middle and lower reaches of the Yangtze River has become a serious problem. Therefore, a test bed for throwing soil after sowing with a wide wheat seed belt was designed, which could complete the functions of straw crushing, straw lateral concentration and uniform sowing at one time. The discrete element simulation model of throwing soil after sowing with a wide wheat seed belt was established with rotary blade shaft speed, soil guide plate angle and soil retaining plate angle as variables. Taking the variation coefficient of wheat sowing depth and variation coefficient of sowing lateral uniformity as evaluation indexes, the effects of three variables on sowing uniformity were analyzed by single factor test and Box–Behnken test. The results of single factor test observed that when the rotating speed of rotary blade shaft was 260–300 rpm, the angle of soil guide plate was 36°–48°, the angle of soil retaining plate was 58°–74° and the experiment of utilizing a soil throwing and covering device with a wide seed belt after sowing revealed a good consistency of sowing depth and lateral uniformity effect. The Box–Behnken simulation experiment showed that the primary and secondary factors affecting the variation coefficient of wheat sowing lateral uniformity were the angle of soil guide plate, the rotation speed of rotary blade shaft, the angle of soil retaining plate and the angle of soil guide plate. When the rotation speed of rotary blade shaft, the angle of soil guide plate and the angle of soil retaining plate were 282.1 rpm, 42.4° and 65.5°, respectively, the soil throwing and covering device after sowing has the best seed-homogenizing effect. At this time, the variation coefficients of sowing depth and lateral uniformity in simulation test and field verification test were 4.35% and 4.57%, respectively, and 12.46% and 12.73%, respectively. The results of field verification test were basically consistent with those of the simulation test, which proved that the results of applying discrete element methods to optimize the soil-throwing device after sowing with a wide seed belt were credible. This study could provide a theoretical reference for the structure optimization of a soil-throwing device after sowing with a wide seed belt.

NanoParticle Flow Reactor (NanoPFR): a tested model for simulating carbon nanoparticle formation in flow reactors

Abstract Flow reactors are widely used to study the formation of various nanoparticles, such as carbon black, soot, nickel, titania, and silica. Such reactors provide well-controlled conditions, making them a favored laboratory tool to investigate the details of particle formation. Here we present NanoParticle Flow Reactor (NanoPFR), a detailed model to simulate nanoparticle synthesis in flow reactors. The model predicts the agglomerate fractal-like morphology and size distribution with a 2-variable sectional population balance model coupled with gas-phase chemistry. The particle formation processes employed in the code are tested using detailed discrete element modeling simulations and then used to predict carbon black formation from ethylene pyrolysis experiments from the literature. The code is a robust flow reactor predictive tool with a strong foundation that can serve as a basis for further development, including the simulation of other nanoparticles formation.

Structure parameter design and bench test research of paddy field blades

Aiming at the problems of high labor intensity and low efficiency in manual operation during the pulping process of rice seedling nursing in thin mud in hilly and mountain areas, this paper designed a new type of paddy field blade for seedling nursing, and utilized a rice nursery pulper to help manual operation complete the pulping process. It created a mathematical model of mud-throwing mass and operating power in the operation process of paddy field blade, and obtained the main structure factors that influenced the mud-throwing mass and operating power of paddy field blade, which included the area of mud splashing board, the angle between the front cutting edge and the mud splashing board, and the inclination angle between the front cutting surface and the mud splashing board. To further analyze the degree of influence of the blade’s main structure parameters on mud-throwing mass and operating power, it used EDEM discrete element simulation software to establish a discrete element simulation model of paddy field blade and mud particle system, performed simulation analysis with the method of orthogonal experimental design, and conducted a bench test for comparison. The results showed that: (1) the degree of influence of the three structure parameters on mud-throwing mass and operating power from large to small in order was the area of mud splashing board > the inclination angle between front cutting surface and mud splashing board > the angle between front cutting edge and mud splashing board; (2) the maximum relative error for mud-throwing mass between simulation analysis and bench test was 4.53%, and that for operating power was 8.67%; and (3) three reference parameters combinations were selected by P2-1/M2 graph, the mud-throwing mass of the three combinations was 40.43%, 27.52% and 0.16% higher than that of the original blade, and the power consumed was 13.99%, 21.83% and 36.65% lower than that of the original blade, indicating that the new paddy field blade had good operating performance.

Design and Test of the Clearing and Covering of a Minimum-Tillage Planter for Corn Stubble

Conservation tillage technology can reduce wind erosion and soil erosion, improve soil fertility, avoid straw burning and relieve ecological pressure. It is an important measure to achieve sustainable agricultural development. In northeast China, there is a large amount of straw covering the ground after the corn machine harvest, which can easily lead to the blockage of the soil-touching parts during no-tillage seeding, affecting sowing quality and crop yield. In order to solve the above problems, the clearing and covering of a minimum-tillage planter for corn stubble was developed. The machine can complete multiple processes, such as seedbed preparation, seeding, fertilization, covering and suppression, straw covering, etc., in a single entity. This paper focuses on the design of the straw cleaning device and uses discrete element method software (EDEM 2018, Altair Engineering, Troy, MI, USA) to establish the straw cleaning device–straw–soil discrete element simulation model. The quadratic-regression orthogonal center-of-rotation combination test method is used to optimize the parameter combination of the machine, using the operating speed, the speed of the knife roller and the penetration depth of the knife as the test factors and using the rate of cleaning straw and the equivalent power consumption as the evaluation index. The results show that each factor has a significant influence on the performance evaluation indices, and the order of influence of each factor on the rate of cleaning straw is operation speed > penetration depth of knife > speed of knife roller, and the order of influence of each factor on the equivalent power consumption is penetration depth of knife > speed of knife roller > operation speed. The optimal combination of parameters is a 5.5–6.2 km/h operation speed, a 500 rpm speed of the knife roller, a 40 mm penetration depth of the knife, a straw-cleaning rate of more than 90% and an equivalent power consumption of less than 8 kW. This study provides technical and equipment support for the promotion of conservation tillage technology in Northeast China.

Calibração de parâmetros de simulação para a erosão eólica fluxo de gás sólido em duas fases em solos áridos e semiáridos

ABSTRACT To construct a coupled simulation model of soil wind erosion and two-phase flow in arid and semiarid regions, the proper contact parameters of the soil discrete element simulation model are obtained based on the angle of repose (AoR) calibration test. The coupled simulation model is established by combining computational fluid dynamics. The response value of the wind speed of sand initiation is used to verify the model’s accuracy. Due to the characteristics of arid and semiarid soils, this paper uses the Hertz-Mindlin with JKR contact model in EDEM software to calibrate the soil parameters based on soil physical tests and designs the Plackett-Burman, steepest climb, and Box-Behnken tests according to Design-Expert software to obtain the soil AoR second-order regression. With the AoR of 33.52° as the target, the best combination of parameters is obtained: soil-soil collision recovery of 0.64, soil-steel static friction coefficient of 0.31, JKR surface energy of 3.302 J m-2. Finally, by using calibrated parameters and the threshold wind velocity as the response value, the wind-sand air-solid two-phase flow test is conducted in ANSYS Fluent and EDEM, with the relative error between the starting wind speed recorded by the high-speed camera in the wind tunnel test and the threshold wind velocity shown in the simulation model calculated to be 8.7%, and the calibrated soil parameters met the requirements of the coupled simulation.

The sleeper group influences on lateral resistance and stability of ballast bed

ABSTRACT The sleeper group, composed of a certain number of rail sleepers, influences the characterization of lateral resistance and the stability of continuous welded rail (CWR). According to full-scale model tests and discrete element model simulation tests of ballast bed, we established a new lateral stability analysis model of CWR considering the effect of sleeper group and resistance sharing characteristics, and compared it with the traditional model. The case analysis shows that the lateral stability analysis result of CWR is safer when considering the effect of sleeper group. When the curve radius is 300 m, the safety margin of the sleeper group model is about 20.8% larger than that of the traditional model. For CWR with potential large lateral displacement in special sections (such as small-radius and large temperature difference), it is advisable to consider the effect of sleeper group for the lateral stability analysis.

Calibration and Verification Test of Cinnamon Soil Simulation Parameters Based on Discrete Element Method

To obtain the discrete element simulation model parameters suitable for the interaction between cinnamon soil and soil-engaging components, the Hertz–Mindlin with JKR contact model in EDEM simulation software was used to calibrate the relevant model parameters of cinnamon soil. Firstly, the particle size distribution, moisture content, volume density, Poisson’ s ratio, shear modulus, and other parameters of the cinnamon soil were measured with cinnamon soil as the research object. Further, taking the stacking angle as the response value, the Plackett–Burman test, the steepest climbing test, and the Box–Behnken were designed by using the Design-Expert software to calibrate and optimize the physical parameters of soil simulation. The optimal parameter combination was obtained: cinnamon soil–cinnamon soil rolling friction coefficient was 0.08, soil JKR surface energy was 0.37 J/m−2, and cinnamon soil–steel static friction coefficient was 0.64. Finally, the discrete element simulation verification test of stacking angle and cutting resistance was carried out under the calibrated parameters. The comparative calculation showed that the relative error between the simulated stacking angle and the measured stacking angle was 0.253%, and the maximum relative error between the simulated cutting resistance and the measured cutting resistance was 10.32%, which was within the acceptable range, indicating the high accuracy and reliability for the calibration parameters. The research results have important reference value for the energy-saving and consumption-reducing design of soil tillage components and provide basic data for the simulation of cutting resistance research of cinnamon-soil-engaging components.

An improved machine learning approach for predicting granular flows

Granular flow is widely practised in many industry processes. The previous prediction methods of granular flow are limited in efficiency, including conventional Discrete Element Modelling (DEM) where direct computation of particle collisions is very time-consuming; and recent machine learning (ML) approach where particle positions were straight predicted and particle–particle and particle–wall collisions were not considered separately, likely compromising the prediction accuracy. In this study, an improved ML approach is developed for predicting granular flows efficiently in terms of computational speed and accuracy. In the proposed ML approach, inspired by Newton’s second law’s concept – from particle acceleration to calculate velocity and then position, a new continuous convolutional neural network (CNN) is established to predict the particles’ accelerations first based on the particle–particle and particle–wall collisions separately, and the particle accelerations are used for calculating particle velocities and finally particle positions. The ML approach is applied to a typical granular flow - particle packing for demonstration. A dataset of 100 scenes of DEM simulations in one scenario is established for network training and examination. The results show that, in long-sequence predictions, the accuracy of the ML approach is three times higher than the previous ML approach. The effects of hyperparameters in the network are quantified. Then the ML approach with the optimized hyperparameters is used in additional three scenarios for further examining the prediction effectiveness. It is indicated that the improved ML approach can satisfactorily capture the morphology of granular flows under three new different scenarios; and the computational cost is only one-seventh compared to the DEM approach under the present conditions. The ML approach provides a simple and time-effective tool for simulating granular flows.

Calibration and analysis of discrete element simulation parameters of Chinese cabbage seeds

ObjectiveTo improve the accuracy of parameters used in discrete element simulation test of Chinese cabbage seeds harvesting process.MethodsFirstly, the key physical parameters of Chinese cabbage seeds were measured. According to the results, the discrete element simulation model was established and the value range of simulation test parameters was determined. Then, the actual repose angle of Chinese cabbage seeds was obtained by physical accumulation test using bottomless conical cylinder lifting method. Plackett-Burman test, steepest climb test, Box-Behnken test and parameter optimization test were carried out in sequence with the actual angle of repose as the response value. Finally, the obtained parameters are verified.Results1. The Plackett-Burman test showed that the seed-seed rolling friction coefficient, the seed-steel rolling friction coefficient, the seed-seed static friction coefficient, and the seed-steel static friction coefficient had significant effects on the repose angle of Chinese cabbage seeds (P<0.05). 2. The optimization test showed that the seed-seed rolling friction coefficient was 0.08, the seed-steel rolling friction coefficient was 0.109, the seed-seed static friction coefficient was 0.496, and the seed-steel static friction coefficient was 0.415. 3. The validation test showed that the repose angle of Chinese cabbage seeds under such parameter was 23.62°, and the error with the repose angle of the physical test was 0.73%.ConclusionThe study show that the discrete element simulation parameters of Chinese cabbage seeds model and calibration are reliable, which can provide reference for the discrete element simulation of Chinese cabbage seeds.

Discrete element simulation model of pulsating hydraulic fracturing considering fatigue damage

Discrete element simulation model of pulsating hydraulic fracturing considering fatigue damage

Discrete element modelling of the yam root–soil complex and its verification

This paper constructs a discrete element simulation model of yam based on a bimodal model and uniform grid coordinates and performs parameter calibration on the simulation model based on three mechanical properties. The bonding parameters are: normal stiffness per unit area 8.0684 × 107 N·m−3, shear stiffness per unit area 2.0314 × 107 N·m−3, critical normal stress 1.2876 × 107 Pa and critical shear stress 8.9623 × 107 Pa. Using the root–soil complex shear test, based on the grey correlation analysis method, a root morphology index with the greatest correlation with the maximum shear force of the yam root–soil complex was obtained. The factor that has the greatest influence on the maximum shear force of the root–soil complex is the total surface area of the root, the correlation degree is 0.77. The root–soil complex bond parameters are as follows: normal stiffness per unit area 5.203 3 × 105 N·m−3, shear stiffness per unit area 2.493 8 × 106 N·m−3, the critical normal stress 1 × 105 Pa and the critical shear stress 5.319 0 × 105 Pa. The accuracy of the simulation model of the yam root–soil complex was verified by comparing the simulation test with the physical test. The relative error of the axial compression rupture pressure value of the yam root–soil complex simulation test and the physical test is 6.63%, the relative error of the displacement value is 8.83%, the relative error of the radial compression rupture pressure value is 6.83%, and the relative error of the displacement value is 6.38%.

Discrete Element Modeling (DEM) simulations of powder bed densification using horizontal compactors in metal additive manufacturing

Efficient packing of the powder bed plays a key role in ensuring high quality of parts printed with Powder Bed Fusion (PBF) based additive manufacturing technologies. This paper presents simulations and analysis of a new technique based on horizontal compactors for improved densification of the spread powder layer. Discrete Element Modeling (DEM) based simulation of this technique shows much improved bed densification and force reduction on the layer underneath, thereby contributing to improved part quality. Results are found to be in excellent agreement with past work. Simulations predict the void fraction distribution as a function of various process parameters. Simulations are carried out to understand the effect of number of particles on stresses acting on the previously printed layer. The technique discussed here is a general one, and may also help analyze other powder-based additive manufacturing processes such as selective laser sintering and binder jetting.

An efficient multiscale bi-directional PBM-DEM coupling framework to simulate one-dimensional aggregation mechanisms

The mesoscale population balance modelling (PBM) technique is widely used in predicting aggregation processes. The accuracy and efficiency of PBM depend on the formulation of its kernels. A model of the volume- and time-dependent one-dimensional aggregation kernel is developed for predicting the temporal evolution of the considered particulate system. To make the developed model physically relevant, the PBM model needs three unknown parameters as input: volume-dependency in collisions, collision frequency per particle and aggregation probability. For this, the microscale discrete element model (DEM) is used. The system’s collision frequency is extracted periodically using a novel collision detection algorithm that detects and ignores duplicate collisions. Finally, a multiscale bi-directional PBM–DEM coupling framework is presented to simulate the aggregation mechanism. PBM and DEM simulations take place periodically to update the particle size distribution (PSD) and extract the collision-frequency, respectively. The coupling framework successfully explains the dependence between the PSD and the collision frequency. Additionally, computational cost of the algorithm is optimized while maintaining the accuracy of the results. Lastly, the accuracy and efficiency of the developed framework are verified using two different test cases. In one of the examples, a simple aggregation is simulated directly inside the DEM for the first time.

PARAMETER CALIBRATION OF DISCRETE ELEMENT SIMULATION MODEL OF WHEAT STRAW-SOIL MIXTURE IN HUANG HUAI HAI PRODUCTION AREA

At present, there is a lack of accurate discrete element simulation model and parameters in the equipment in Huang Huai Hai double cropping production area, which hinders the optimization and improvement of equipment operation effect. In this paper, the discrete element method is used to study the interaction between soil-touching components and wheat straw-soil mixture to improve the performance of equipment. Firstly, the Hertz-Mindlin with JKR Cohesion contact model is selected for the wheat straw-soil mixture to calibrate the parameters. Then, the method of combining physical test and simulation test is used to calibrate the parameters, the cylinder lifting method is used to determine the buildup angle of wheat straw soil mixture, and the Plackett-Burman screening method and the steepest climbing test are used to determine the optimal combination range of soil-straw static friction coefficient, soil-straw dynamic friction coefficient and soil-soil dynamic friction coefficient contact model parameters. Using Box-Behnken optimization research and development of key components such as soil contact of seedbed preparation test, the regression equation of the stacking angle of wheat straw soil mixture was obtained, and the variance and interaction effect of the regression model were analysed. The regression model was used to find the optimal solution in Design-Expert software with an angle of repose of 41.23°, which yielded a soil-straw static friction factor of 0.072, a soil-straw dynamic friction factor of 0.78, and a soil-soil dynamic friction factor of 0.068, with an angle of repose error of 1.43%, indicating that the contact model parameters are reliable, and the parameters can provide a reference and theoretical basis for the study of the key components of the seedbed preparation equipment such as touching soil in the Yellow and Huaihai Sea two-maturity zone.

Ultrasonic Coda Wave Experiment and Simulation of Concrete Damage Process under Uniaxial Compression

Using the coda wave interferometry (CWI) method to obtain the ultrasonic coda wave characteristics of loaded concrete is an important method to evaluate the mechanical response of concrete. In this paper, the ultrasonic coda wave characteristics of C40–C70 concrete specimens (four strengths of concrete) under uniaxial compression were tested by laboratory experiments. Furthermore, to clarify the relationship between the internal damage process of concrete and the change rate of coda wave velocity, an ultrasonic coda wave discrete element simulation model combined with digital image processing technology was established. The results show that the coda wave is very sensitive to small changes in the compressive damage to concrete, and the change in coda wave velocity can correspond to the development process of concrete damage. This research is conducive to a better understanding of the complex material behavior of compressive concrete and proves the feasibility of ultrasonic field simulation and processing by using numerical simulation images of concrete damage.

Research on discrete element modeling and numerical simulation of cutting rock behavior under impact load

AbstractCombining well‐drilling hammers with polycrystalline diamond compact bits to break rock under cutting load and impact load is an effective way to improve drilling efficiency. Although impact load can enhance the cutting efficiency of the cutter, excessive impact can also cause the cutter to be subjected to additional vibrations, which can decrease its working life. Knowledge of laws governing the changes in the cutting force of the cutter under impact load is essential for the design and selection of well‐drilling hammers. Based on rock scratch tests and finite element rock cutting model, a discrete element modeling (DEM) rock cutting model was established to analyze the rock breaking and cutting force. Then, the material parameters of rock samples were determined, and the simulation parameters were corrected. Finally, a DEM rock cutting model under an impact load was established. The results showed that when there was an obvious difference between the average cutting force and mean peak cutting force, which corresponded to the rock‐breaking transition from ductile to brittle, with introduction of the impact load leading to an earlier transition. The cutting force variance was proportional to the impact amplitude, and the increase in the cutting force variance became more obvious when the static load exceeded the critical transition weight. When the ratio of the impact amplitude to the static load was greater than 50%, the mean and variance of the cutting force increased rapidly. Under the same impact amplitude, the impact frequency had little effect on the average cutting force, but a higher frequency could significantly reduce the variance of the cutting force under a high static load (i.e., it could alleviate the fluctuation of the cutting force). These results provide a reference for the selection of well‐drilling hammers and optimization of the impact load.

Simulation and Experiment of the Spiral Digging End-Effector for Hole Digging in Plug Tray Seedling Substrate

Usually the planters used in agricultural machinery face two problems: The planters have to spread the soil twice using the tray seed planter, and it is difficult for them to dig the holes before planting. This study has designed a spiral digging end-effector to dig holes in parallel effectively and quickly so that the seeds can be planted in the holes easily. A spiral digging end-effector was designed with five spiral bits, a synchronous belt, a cylinder, a gear motor, and a connecting plate based on the tray size and the pumpkin seed characteristics. Before the optimization of the end-effector’s parameters, the substrate discrete element model parameters were calibrated using the method of “material funneling” applied for the EDEM discrete element model simulation. The contact parameters and model parameters (substrate–substrate static friction coefficient, substrate–substrate rolling friction coefficient, and surface energy) that have significant impacts on the substrate AOR (angle of repose) were selected by applying the Plackett–Burman Design and the path of steepest ascent method, and their respective optimal value range were determined. The optimal parameter values were obtained through the Central Composite Design response surface analysis test, and the parameters of the spiral digging end-effector were optimized combining the substrate particle simulation. The verification test results indicate that the substrate discrete element model parameters were accurate and reliable if the substrate static friction coefficient was 0.427; the substrate rolling friction coefficient was 0.039, and the surface energy was 0.228. When the cone angle is 30°, the spiral angle is 80°, and the rotational speed is 240 r/min, the section width at the hole depth of 13 mm is 23.1 mm, and the particle overflow proportion is about 2.05%. Compared with the protrusions penetrating end-effector, soil porosity is increased, and soil aeration is improved. Therefore, the spiral digging end-effector can effectively and quickly dig holes in the seedling substrate and can sow pumpkin seeds, which provides a research basis for the design and improvement of automatic pumpkin seed sowing equipment.

Discrete element modeling of aggregate shape and internal structure effects on Weibull distribution of tensile strength

Many soil processes and functions, including carbon storage, water and element cycling, and crop productivity, are directly or indirectly affected by soil aggregates. As a key property, aggregate tensile strength is usually quantified by the Weibull distribution. This distribution was found to depend on soil texture, organic matter content, and aggregate shape; however, effects of cementing agents (i.e., clay mineral and organic compounds) on aggregate tensile strength cannot be empirically studied independent of shape. The objective was to apply Discrete Element Modeling (DEM) to simulate the rupture of soil aggregates of different shapes but the same assumed distributions of cementing agents. The hypothesis was that the Weibull modulus of aggregate tensile strength could be used to describe the heterogeneity of the particle binding forces within the aggregate. Multiple DEM simulations of aggregate rupture were carried out for sets of randomly generated binding force distributions between particles of the same diameter. Aggregate properties and shapes were obtained from those observed in arable Gleyic Cambisol topsoil from plots with and without vegetation of a soil compaction trial; additional aggregate shapes were simulated to increase the predictive range. The simulation results showed that (i) the sensitivity of Weibull modulus of aggregate tensile strength to the heterogeneity of particle binding force distribution increased with aggregate sphericity, (ii) the value of the Weibull modulus decreased with increasing heterogeneity of this distribution, and (iii) internal heterogeneity also reduced the crack surface area produced by aggregate rupture. Results corresponded to friability theory implying that small values of Weibull modulus indicated more complex soil structural organization. The DEM simulations could help explaining complex interactions between aggregate shape cementing agents and stability. Our DEM approach also uncovered the importance of Weibull modulus to assess structural features of soil aggregates and to describe the heterogeneity of the particle binding forces within the aggregate.

Design optimization and scale-up characteristics of a double-helical ribbon reactor for biomass catalytic pyrolysis

Pyrolysis characteristics are closely related with the inner mixing performance of biomass and biochar particles in agitated biomass catalytic pyrolysis reactors. In this study, a novel double-helical ribbon reactor was designed for biomass catalytic pyrolysis. DEM (Discrete Element Model) simulations were performed to optimize the structure and operating conditions. Model calibration and validation experiments were firstly conducted. The effects of structural parameters and rotation speed on mixing performance were further explored. The results showed that the mixture homogeneity was closely related to the impeller outer diameter and rotation speed, while the mixing rate could be optimized by adjusting the inner diameter and pitch. The optimal operation condition showed adequate mixing in the axial and radial directions. Besides, the scale-up analysis demonstrated that similar mixing performance was presented at the same Froude number. Finally, the correlations of mixing characteristics provided a theoretical reference for industrial reactors design.

Solids lateral mixing and compartmentalization in dynamically structured gas–solid fluidized beds

An adequate use of gas pulsation can create an ordered, dynamically structured bubble flow in a bed of Geldart B particles. A structured bed is more homogeneous, responds to external control and is scalable. While earlier studies have focused on describing the self-organization of the gas bubbles, the solid mixing and gas–solid contact patterns have remained unclear. In this work, the solids circulation and mixing behavior in structured and unstructured beds at various pulsation frequencies are compared with a traditional fluidized bed operation. The degree of lateral mixing is hereby quantified through an effective lateral dispersion coefficient extracted from CFD-DEM (discrete element modelling) simulations in a thin fluidized bed system. Mixing shows major quantitative and qualitative differences amongst the investigated cases. The coordinated motion of the gas bubbles wraps the solid flow into a series of compartments with minimal interaction, whereby effective lateral dispersion coefficients are an order of magnitude lower than in an unstructured operation. More importantly, unlike a traditional bed, dispersion in a structured bed is driven by advection and is no longer a diffusive process. Compartmentalization decouples the time scales of micro- and macromixing. Every pulse, the compartments rearrange dynamically, causing a level of local axial mixing that is scale-independent. While further work is necessary to fully understand the compartmentalization at a larger scale, the circulation described here indicates that a dynamically structured bed can provide a tight control of mixing at low gas velocities and a narrower distribution of stresses in the solid phase compared to traditional devices.