Coupled Computational Fluid Dynamics Discrete Element Method Research Articles

Pulsation effects on mixing behaviour of binary particles with different densities in supercritical water fluidized bed reactors: A CFD-DEM study

A coupled computational fluid dynamics - discrete element method (CFD-DEM) model for simulating supercritical water fluidized bed reactors (SCWFBR) is established and verified using the previous correlations based on experimental data. The CFD-DEM model is then adopted to investigate the pulsation effects on the mixing behaviour of binary particles with different densities in the SCWFBR. Numerical results show that external energy pulses can be effective in promoting the mixing of binary particle systems with different densities in SCWFBR which cannot be achieved by simply increasing the flow rate constantly. Within the current parameter range: low-frequency pulses are favored to promote particle mixing rather than high-frequency pulses, and an optimal frequency exists. The role of low amplitudes in influencing mixing degree is slight, but the particle mixing degree can be greatly enhanced by increasing the pulse amplitude beyond a certain value. The mechanism that pulsed inlet fluid promotes particle mixing is to raise the heavy particles which are inclined to stay at low positions during the fluidization. The Fast Fourier Transform (FFT) method to predict the optimal frequency established for size-induced segregation can be applicable to solve the problem of the density-induced segregation.

Simulation of Hydrate Particles Aggregation and Deposition in Gas-Dominated Flow

Summary Owing to low-temperature and high-pressure production environments, hydrate generation, accumulation, and deposition are prone to occur in deepwater oil and gas production wells and transportation pipelines, leading to pipeline blockage and threatening the safety of oil and gas production. To explore the aggregation mechanism and deposition law of hydrate particles in the main gas diversion pipeline, this study considered the adhesion effect of hydrate particles and established a hydrate particle aggregation and deposition model based on theory and experiments. The coupled computational fluid dynamics-discrete element method (CFD-DEM) is used in the simulation calculation. The simulation results were compared with the relevant experimental results, and maximum and average errors of 9.48% and 4.56% were observed, respectively. It was found that the main factor affecting the aggregation of hydrates is the adhesion between particles. As the subcooling temperature increased, the aggregation and adhesion of the hydrate particles increased to varying degrees. The tangential adhesion force between the hydrate aggregate particles was significantly greater than the normal adhesion force, and the adhesion force between the particles gradually increased from the surface to the interior of the aggregates. The coordination number of the hydrate particles can quantitatively characterize the degree of aggregation and is affected by many factors, such as adhesion. By studying the particle coordination number, the evolution of hydrate accumulation and deposition under different conditions can be summarized. Based on the simulation results, the mathematical relationship between different dimensionless numbers and hydrate deposition ratio (HDR) was calculated, and an expression that can predict the HDR was obtained, with an average relative error of 10.155%. This study provides a theoretical basis for predicting the aggregation and deposition of hydrate particles in gas-dominated systems and a reference for the development of hydrate prevention and control plans.

CFD–DEM modelling of the infiltration of non-spherical slurry particles in granular soils

The slurry filtration process at an excavation surface plays an important role in supporting pressure transmission, which is crucial to the stability of a tunnel face during slurry shield tunnelling. In this paper, a series of coupled computational fluid dynamics (CFD)–discrete element method (DEM) numerical simulations were carried out to model the slurry filtration column test. Oblate spheroids of varying aspect ratios were adopted to represent slurry particles. A simplified pitching torque model was implemented to better simulate the motion of slurry particles. The pressure distribution, void fraction, permeability and orientations of the particles were analysed as the aspect ratio was systematically changed. The pressure distribution, void fraction and the permeability within a stratum are highly dependent on the aspect ratio of the particles. Particles with larger aspect ratios tend to effectively seal infiltration channels and transfer slurry pressure to effective pressure, thereby helping to maintain stability at the tunnel face. This research study explores how particle shape impacts the slurry infiltration procedure and the microstructure of the filter cake.

Fracture sealing performance of granular lost circulation materials at elevated temperature: A theoretical and coupled CFD-DEM simulation study

Lost circulation is a common downhole problem of drilling in geothermal and high-temperature, high-pressure (HTHP) formations. Lost circulation material (LCM) is a regular preventive and remedial measure for lost circulation. However, conventional LCMs seem ineffective in high-temperature formations. This may be due to the changes in the mechanical properties of LCMs and their sealing performance under high-temperature conditions. To understand how high temperature affects the fracture sealing performance of LCMs, we developed a coupled computational fluid dynamics-discrete element method (CFD-DEM) model to simulate the behavior of granular LCMs in fractures. We summarized the literature on the effects of high temperature on the mechanical properties of LCMs and the rheological properties of drilling fluid. We conducted sensitivity analyses to investigate how changing LCM slurry properties affected the fracture sealing efficiency at increasing temperatures. The results show that high temperature reduces the size, strength, and friction coefficient of LCMs as well as the drilling fluid viscosity. Smaller, softer, and less frictional LCM particles have lower bridging probability and slower bridging initiation. Smaller particles tend to form dual-particle bridges rather than single-particle bridges. These result in a deeper, tighter, but unstable sealing zone. Reduced drilling fluid viscosity leads to faster and shallower sealing zones.

Numerical Study on High Throughput and High Solid Particle Separation in Deterministic Lateral Displacement Microarrays

Deterministic lateral displacement (DLD) is a high-resolution passive microfluidic separation method for separating micron-scale particles according to their size. Optimizing these microsystems for larger throughputs and particle concentrations is of interest for industrial applications. This study evaluates the limitations of the functionality of the DLD separation principle under these specific conditions. For this reason, different particle volume fractions (up to 11%) and volumetric flow rates (corresponding to Reynolds numbers up to 50) were varied within the DLD microsystem and tested in different combinations. Resolved two-way coupled computational fluid dynamics/discrete element method (CFD-DEM) simulations including spherical particles were performed. The results show a general increase in the critical diameter with increasing volume fraction and decreasing separation efficiency. The largest tested Reynolds number (Re = 50) results in the highest separation efficiency, particularly at low volume fractions, and is only slightly less efficient than low Reynolds numbers as the volume fraction increases. The results indicate that by limiting the volume fraction to a maximum of 3.6%, the flow rate and the associated separation rate can be increased while maintaining a high separation efficiency.

Macro–microscopic mechanism of suffusion in calcareous sand under tidal fluctuations by coupled CFD-DEM

Numerous offshore transportation infrastructures built with delicate calcareous sand (CS) experience intricate seepage conditions caused by tidal fluctuations. Traffic loads can cause substantial particle crushing, leading to mass loss and subsequent settlement. This paper presents a numerical analysis of suffusion mechanisms in three representative volume elements (RVEs) under cyclic seepage using the coupled computational fluid dynamics-discrete element method (CFD-DEM). The microscopic parameters of CS are calibrated by comparing the results with direct shear experiments. The effect of particle breakage on cyclic suffusion can be assessed by varying breakage ratios of crushed soil. Several suffusion tests under periodic seepage are conducted to investigate the fines migration behavior and examine the contact characteristics, with a particular focus on the middle element of the three RVEs. Test results confirm that mass loss of the sample is intensified by particle breakage but is effectively inhibited under high-stress conditions. Fine particles exhibit different migration behaviors in this study compared to those observed under unidirectional seepage, including reverse migration. The change in connectivity of the particle assembly during cyclic seepage indicates a gradual weakening of its overall stability. Lastly, the anisotropy of the normal contact force distribution exhibits a significant increase as more particles are eroded.

The Development of a Multiphysics Coupled Solver for Studying the Effect of Dynamic Heterogeneous Configuration on Particulate Debris Bed Criticality and Cooling Characteristics

For a sodium-cooled fast reactor, the capability for stable cooling and avoiding re-criticality on the debris bed is essential for achieving in-vessel retention when severe accidents occur. However, an unexploited uncertainty still existed regarding the compound effect of the heterogeneous configuration and dynamic particle redistribution for the debris bed’s criticality and cooling safety assessment. Therefore, this research aims to develop a numerical tool for investigating the effects of the different transformations of the heterogeneous configurations on the debris bed’s criticality/cooling assessment. Based on the newly proposed methodology in this research, via integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) and Monte-Carlo-based Neutronics (MCN), the coupled CFD–DEM–MCN solver was constructed with the originally created interface to integrate two existing codes. The effects of the different bed configurations’ transformations on the bed safety assessments were also quantitively confirmed, indicating that the effect of the particle-centralized fissile material had the dominant negative effect on the safety margin of avoiding re-criticality and particle re-melting accidents and had a more evident impact than the net bed-centralized effect. This coupled solver can serve to further assess the debris bed’s safety via a multi-physics simulation approach, leading to safer SFR design concepts.

Exploring the role of nasal hair in inhaled airflow and coarse dust particle dynamics in a nasal cavity: A CFD-DEM study

This study presents a novel coupled computational fluid dynamics-discrete element method (CFD-DEM) model for simulating airflow and inhaled particle dynamics in the nasal cavity, considering the fluid-structure interactions between nasal hair and airflow, which are often overlooked in existing CFD simulations. The CFD-DEM model, based on a virtual nasal cavity geometry, represents nasal hairs as flexible fibers implanted on the inner wall of the nasal cavity. Inhaled air-particle transport dynamics were simulated in the presence of nasal hairs with three different diameters (40, 95, and 120 μm), and the results were compared with simulations without nasal hairs. Polydisperse particles with diameters ranging from 5 to 15 μm, aligning with global coarse dust statistics, were inhaled at flow rates between 216 mL/s and 630 mL/s, representing human nose breathing conditions from rest to exercise. The CFD-DEM simulation results indicate that the differences in deposition fraction predictions between cases with and without nasal hairs exceed 20% for particle size ranges corresponding to impaction parameter values between 3E+3 and 2E+4 μm2cm3/s. This emphasizes the importance of accounting for nasal hair interactions in accurately simulating inhaled particle transport dynamics within the nasal cavity. Thinner nasal hairs, more flexible than thicker ones, lead to more significant deformation and allow more particles to penetrate the nasal vestibule without being trapped. Additionally, thinner hairs occupy a smaller cross-section area in the nasal vestibule, resulting in lower filtration capability due to decreased particle deposition from interception and inertial impaction. Thicker nasal hairs trap more coarse dust particles (> 5 μm) effectively than thinner nasal hairs. Moreover, as the nasal hair diameter increases, particle deposition on the nasal cavity wall decreases. Nasal hairs demonstrate higher efficiency in trapping smaller particles. In conclusion, the CFD-DEM model, capable of modeling nasal hair motion, can serve as a next-generation in silico tool for investigating biofluid dynamics in the nasal cavity.

Effect of particle shape and bedding angle on suffusion in gap‐graded granular soils by coupled CFD‐DEM method

AbstractThe natural deposition of soils results in significant fabric anisotropy, and its influence on suffusion remains unclear. In this study, a series of gap‐graded soil samples with different particle shapes and bedding angles are generated and implemented into the coupled computational fluid dynamics‐discrete element method (CFD‐DEM) simulations to investigate the migration of fine particles within the coarse grain matrix. Macroscopic results, including mass loss, void ratio variation, and soil deformation, as well as microscopic particle trajectory, force chain network, and contact orientation are analyzed. In addition, drained triaxial tests on samples before and after erosion are carried out. All results turn out that the greater the bedding angle, the more severe the loss of fines and the more significant the soil deformation. Three different migration characteristics can be identified according to soil anisotropy degree, that is, when the bedding angle is 0°, the migration of fine particles remains relatively stable; when the bedding angle is 30° and 60°, the particle migration shows a gradual change throughout the erosion; when the bedding angle is 90°, the fine particles migrate significantly in the very early stages of suffusion. Besides, the aspect ratio (AR) of the particle is found to be beneficial for both erosion resistance and soil strength.

Coupled CFD-DEM Simulation of Seed Flow in Horizontal-Vertical Tube Transition

A series of computational fluid dynamics–discrete element method (CFD-DEM) simulations were applied to seed flow in horizontal-vertical 90-degree elbows. The performance of one-way and two-way CFD-DEM coupling methods was compared. Additionally, simulated seed velocities were compared to the current pneumatic conveying theory for each coupling method. Simulated field peas (Pisum sativum) were pneumatically conveyed to study the effect of air velocity (20, 25, and 30 m/s), seed rate (0.07, 0.21, and 0.42 kg/s), elbow diameter, D, (48.3, 60.3, and 72.4 mm), and elbow bend radius (1.5D, 2.5D, 3.5D, and 4.5D) on seed attributes (trajectory, velocity, and force). Results showed that seed velocity was significantly different between one-way and two-way coupling. Both methods resulted in nearly identical seed trajectory and force. Overall, simulated seed velocities had a strong correlation to values calculated through the current pneumatic conveyance theory. Dimensional analysis revealed that seed contact force was proportional to the elbow diameter to the power of 0.26 and inversely proportional to the elbow bend radius to the power of 0.5. Simulation results indicated that one-way coupling could be suitable to describe seed flow when two-way coupling may not be possible or practical.

Influence of the Spiral Angle of the Blade on the Material Loading Characteristics of the Slurry Pump

To study the effect of rotational speed on the internal flow characteristics and operating performance of a deep-sea mining slurry pump, a new type of slurry pump delivery system with changing vane helix angle is adopted in this paper. Based on the coupled computational fluid dynamics-discrete element method (CFD-DEM), the realizable k-ɛturbulence model and SIMPLE algorithm are applied to numerically simulate the solid-liquid two-phase flow field in the slurry pump to study the effect of rotational speed on the flow characteristics and distribution of particles in the slurry pump. The results show that with the increase in rotational speed, the separation of the boundary layer at the impeller runner is promoted, which weakens the particle overflow capacity and increases the hydraulic loss. The impact at the inlet of the guide vane runner is more violent. The fluid flow separation at the inlet is suppressed. The overflow capacity is increased and the hydraulic loss is weakened. With the increase in rotational speed, the more the average number of collisions between particles and vanes in each time period, the more the particles collide with the impeller and space. The collision probability and collision speed of the guide vane overflow parts become larger, thus laterally reflecting that the larger the rotational speed, the greater the wear rate of particles on the blade is.

Numerical investigation on the fracture-bridging behaviors of irregular non-spherical stiff particulate lost circulation materials in a fractured leakage well section

Particle bridging is considered crucial for controlling fracture leakage. A deep understanding of fracture-bridging behavior determines the correct selection of lost circulation materials (LCMs) for fractured leakage. Existing physical and numerical analyses have failed to fully reveal the process of irregular non-spherical particles flowing into a fracture from a wellbore. To investigate the fracture-bridging process, a coupled computational fluid dynamics-discrete element method (CFD-DEM) simulation model was established in this study. The model was verified with a published fluidized bed case and visual fracture bridging simulation experiments. Using digital image technology, 3D discrete element particle models were regenerated from the actual irregular non-spherical stiff particulate LCMs. This allows the analysis of particle size conditions under which particles of different shapes can effectively enter the fractures. The concept of bridging capacity was defined to quantitatively evaluate the bridging effect of LCMs. Based on the numerical simulation results, the bridging patterns of LCM particles were systematically analyzed. The results show that the more uniform the size in each direction of a particle is, the easier it is to enter the fracture. The flatter the particle, the smaller the equivalent particle diameter allowed to enter the fracture. The bridging capacity of irregular blocky particles reached its maximum when the ratio of the particle size to fracture opening was 0.5–0.7. Compared with the blocky particles, flaky particles in fractures exhibited a lower bridging capacity. The bridging pattern of irregular blocky particles in the fracture was single-particle bridging, and the flaky particles had both single-particle and dual-particle bridging patterns. The method and finds proposed in this paper can explain the difference of bridging behaviors of particles with different shapes on the particle scale, and provide a scientific basis for the selection of LCMs in a fractured leakage well section.

Effect of particle shape on the hydrodynamics of gas-solid fluidized bed

Non-spherical particles are common in industrial applications such as coal gasification and biomass combustion. The present work employs a coupled Computational Fluid Dynamics – Discrete Element Method (CFD-DEM) approach to numerically investigate the particle shape effect on the hydrodynamics of a rectangular gas-solid fluidized bed. The CFD-DEM model capability is tested by comparing the mean horizontal and vertical velocities and pressure drop against the National Energy Technology Laboratory (NETL) experimental data. The effect of different numerical parameters (time step, grid size, discretization technique) on the predicted data is also studied. A grid size of three particle diameters and a 2nd Superbee discretization scheme are selected to run the simulations based on the numerical accuracy and simulation time. Seven different drag models are utilized to model the particle-fluid interaction. Further, simulations are conducted using the Di Felice-Ganser drag model for five different sphericities. A strong relationship between sphericity and fluidization behavior is noted. At the constant superficial gas velocity of 2.19 m/s, the fluidization behavior is changed from bubbling to a turbulent regime when the sphericity decreases from 1 to 0.42.

CFD-DEM simulation of sand erosion into defective gravity pipes under constant groundwater table

As sewer pipes age, cracks and other forms of structural damage may develop leading to soil infiltration into the pipes that can cause sinkholes and damage the overlying roads and moving vehicles. The fluctuations in the groundwater table following snow melt or heavy rainfall events can exacerbate soil erosion posing risk to the surrounding infrastructure. To understand and adequately characterize erosion in such cases, microscale analysis of both sand and water is needed to resolve the complex interactions around the pipe defects. In this study, a detailed numerical investigation is carried out using a series of coupled Computational Fluid Dynamics-Discrete Element method (CFD-DEM) simulations to evaluate the effects of groundwater table, crack size, defect angle, and the height of sand fill above the pipe on erosion. It is found that raising the groundwater table accelerates erosion only to a certain limit, above which, raising the groundwater level does not have a tangible effect on erosion. This helps explain some of the misunderstandings reported in previous investigations regarding the effect of water level on the rate of erosion. With respect to the location of defects, it was found that, when groundwater is involved, the erosion rate is fastest when the defect is located at the pipe crown. However, inclined defects ultimately resulted in a larger spatial extent of eroded mass. In addition, the thickness of the sand fill above the pipe was found to have little effect on the rate of erosion as a freefall arch regime was dominant in all simulations. Finally, simplified relationships were developed for estimating the total eroded mass for given sand properties, defect geometry, and location of the groundwater table.

CFD-DEM modeling of geotextile clogging in tunnel drainage systems

In this study, a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) method we used to investigate the hydraulic deterioration of a geotextile due to clogging in tunnel drainage systems. Initially, a framework was developed to generate and test a numerical representation of a typical non-woven geotextile. Following model validation, we carried out parametric analysis to examine the effect of fine content, crack angle, and groundwater inflow. The results showed a general trend of pressure increase associated with increasing both the crack angle and fine content. This increase was found to decay at larger crack angles and high content of fines. Interestingly, increasing groundwater inflow was found to had minimal effect on the final deposition of the clogging particles. Finally, an approximate semi-analytical model was developed to describe the pressure increase due to clogging. The model was able to provide a good match with the data obtained from the numerical analysis.

Numerical investigation on fluidization characteristics of binary particles in supercritical water fluidized bed reactor under pulsed conditions

The fluidization properties of binary particles in a supercritical water fluidized bed reactor (SCWFBR) are numerically investigated based on coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations. The accuracy and effectiveness of the CFD-DEM model is firstly validated via previously published experimental data. Then, the model is adopted to study the effect of flow velocities and sinusoidal pulse on the mixing of the binary particles. Numerical results show that it is effective to promote mixing of binary particles in SCWFBR by introducing external energy pulses, which cannot be achieved by simply increasing the flow velocities without pulses. Compared to high frequency pulses, low frequency pulses are more effective in promoting mixing. Within the parameters considered here, it is also found that the pulse amplitude is almost positively correlated with the effect on the promotion of particle mixing when it is smaller than the fixed flow velocity. In addition, an efficient and economical method based on Fast Fourier Transform (FFT) on the bed pressure drop is given to determine the optimal pulse frequency, which can prevent the waste of manpower and the physical resources from happening. This study can provide technical guidance to achieve optimal mixing of binary particles in SCWFBR and offer theoretical support for the design and optimization.

Modelling flocculation using CFD-DEM in a turbulent flow, with reference to “Particle flocculation in a stirred tank: A microscopic test by coupled CFD-DEM approach” by Wang et al.

The coupled Computational Fluid Dynamics – Discrete Element Method (CFD-DEM) modelling technique is a potentially very powerful one for simulating the flocculation process (as well as many other coupled particulate-fluid flow phenomena). However, great care must be used when the fluid flow is turbulent, since RANS (Reynolds averaged Navier-Stokes) turbulence models cannot be used for the CFD part of the simulation since they are incompatible with the DEM component of the model. This is because DEM simulation requires the instantaneous fluid velocity to be available at each particle location at each time-step, and this information is not given by a RANS CFD simulation. A recent example is given of this erroneous simulation technique, together with examples of more rigorous alternative methods.

Insight into bubble-to-emulsion mass transfer of an isolated clouded bubble in an incipiently fluidized bed

When the gas flowing out of the bubble in a gas–solid fluidized bed is recirculated to the bottom and then re-enters the bubble, a clouded bubble is formed. Or else, the gas directly flows into the emulsion phase, forming the cloudless bubble. Owing to different flow patterns between clouded bubble and cloudless bubble, there are different mechanisms for the bubble-to-emulsion mass transfer process. In this work, mass transfer behaviors of an isolated clouded bubble are studied by a coupled computational fluid dynamics-discrete element method (CFD-DEM). The mass exchange contributions by convection and diffusion are evaluated. The results reveal that the diffusion-induced mass transfer is more significant for the clouded bubble than that for the cloudless bubble. The predicted mass transfer coefficient considering the local gas concentration in the emulsion phase shows a good agreement with the correlation prediction by Kunii and Levenspiel (1991). Moreover, the impact of the non-isothermal condition is also explored. When the hot tracer gas is injected into the cold bed, a reverse convective mass transfer is presented at the start stage after the gas injection owing to a strong driving force of gas suction in the bubble wake. Whereas for the tracer gas injection at the room temperature into the bed with pre-heated particles, the mass transfer by diffusion is enhanced and the reverse mass transfer process disappears.

Removing cuttings from inclined and horizontal wells: Numerical analysis of the required drilling fluid rheology and flow rate

Inclined and horizontal wells are prone to the accumulation of drilling cuttings. Determination of the optimal drilling parameters that facilitate cuttings removal is a key problem. Existing experimental, theoretical and field-based empirical analyses of the hole cleaning problem have failed to fully reveal the processes of cuttings transport, settlement, and accumulation concerning drilling string rotation in large annuli with high-density non-Newtonian drilling fluids. In this study, a coupled computational fluid dynamics-discrete element method (CFD-DEM) simulation model of the interaction between cuttings and drilling fluid was established. This allows the influences of well inclination, drill pipe rotational rate, flow rate, fluid density, and rheological properties on hole cleaning efficiency to be analyzed. A multi-parameter correlation equation between wellbore cleaning efficiency and wellbore size, inclination angle, drill string eccentricity, drill string rotational speed, rate of penetration, cuttings size, flow rate, and fluid density was obtained using dimensional analysis and multivariate nonlinear regression of simulation data. Finally, with consideration of wellbore cleaning characteristics, formation pressure bearing capacity, and pump condition constraints, the proposed multi-parameter correlation model was used to provide optimal wellbore cleaning parameters. The cleaning efficiency of horizontal wells is lowest in the inclined section. Hole cleaning efficiency increases significantly with drill pipe rotational rate, flow rate, and 6 RPM Fann dial reading. The proposed model can correlate hole cleaning efficiency with the 6 RPM Fann dial reading of drilling fluid and flow rate. At a given hole cleaning efficiency, the required minimum flow rate decreases with increases in the 6 RPM Fann dial reading. Similarly, the required minimum 6 RPM Fann dial reading decreases with increases in flow rate. The models and design layout proposed in this paper provide a new approach to solving hole cleaning parameter design problems in highly inclined and horizontal wells.

CFD-DEM study on fluidization characteristics of gas-solid fluidized bed reactor containing ternary mixture

Coupled computational fluid dynamics - discrete element method (CFD-DEM) simulations are carried out to investigate the fluidization characteristics of gas-solid fluidized bed reactor (FBR) containing ternary particles (spheres, ideal and elongated cylinders, the latter two are rod-like particles). The mixing efficiency, velocity distribution, orientation distribution and height change of different particles during the mixing process are fully investigated and discussed. Numerical results show that when the superficial gas velocity is low, the mixing efficiency would decrease with the increase of the volume fraction of elongated cylinders due to the inter-locking. However, the discrepancy of mixing degree induced by particle shape can be weakened by increasing the superficial gas velocity. Elongated cylinders become quite active when the inter-locking is broken with more uncertainty in their motion. Ideal cylinders prefer to be horizontal at all the superficial gas velocities considered but elongated ones only show similar behavior at low superficial gas velocities. When the superficial gas velocity is high, the time-averaged orientation of elongated cylinders becomes quite uniform. The inclined angle of both ideal and elongated cylinders decreases with the increase of height and large inclined angles are found at the two lower corners of the reactor. The ideal cylinders turn to be more vertical when the position moves to the central line of the FBR. In the lower half of the bed material, the elongated cylinders prefer to be horizontal in the near-wall region but more vertical in the center of the upper half. Within the range of currently considered superficial gas velocities, the overall mixing degree of the ternary mixture can be enhanced by increasing the superficial gas velocity both in efficiency and stable mixing degree. The findings can be very useful to guide the improvement of existing reactors and the design of novel ones.Numerical simulation; Fluidization; Ternary granular mixture; Mixing behavior; Rod-like particles.