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 circulatio...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.展开更多
Accurately predicting heat flux in coarse-grained CFD-DEM simulations is a significant challenge.Specifically,the rates of fluid-particle heat exchange,the effective thermal conductivity of a bed of particles,as well ...Accurately predicting heat flux in coarse-grained CFD-DEM simulations is a significant challenge.Specifically,the rates of fluid-particle heat exchange,the effective thermal conductivity of a bed of particles,as well as radiative heat transfer rates are difficult to predict.By using a novel algorithm,we significantly improve the accuracy and stability of such simulations by using a heat exchange limiter.This limiter enables realistic predictions even at time steps that are three orders of magnitude larger than a typical fluid heat relaxation time.Additionally,view-factor-based corrections for radiative heat exchange computations are developed.These corrections ensure an effective thermal bed conductivity with less than 3%error for a coarse-graining ratio of 10.The applicability of the P1 radiation model in coarse-grained settings is also examined,leading to recommendations for the CFD grid resolution to ensure accurate predictions.Our methods significantly enhance stability,accuracy,and computational efficiency,making coarse-grained CFD-DEM simulations more viable for industrial applications.These advancements enable more reliable modeling of high-temperature processes,accelerate optimization studies,and enable virtual equipment design of such processes.展开更多
BACKGROUND Orthopaedic surgical education has traditionally depended on the apprenticeship model of“see one,do one,teach one”.However,reduced operative exposure,stricter work-hour regulations,medicolegal constraints...BACKGROUND Orthopaedic surgical education has traditionally depended on the apprenticeship model of“see one,do one,teach one”.However,reduced operative exposure,stricter work-hour regulations,medicolegal constraints,and patient safety concerns have constrained its practicality.Simulation-based training has become a reliable,safe,and cost-efficient alternative.Dry lab techniques,especially virtual and augmented reality,make up 78%of current dry lab research,whereas wet labs still set the standard for anatomical realism.AIM To evaluate the effectiveness,limitations,and future directions of wet and dry lab simulation in orthopaedic training.METHODS A scoping review was carried out across four databases-PubMed,Cochrane Library,Web of Science,and EBSCOhost-up to 2025.Medical Subject Headings included:"Orthopaedic Education","Wet Lab","Dry Lab","Simulation Training","Virtual Reality",and"Surgical Procedure".Eligible studies focused on orthopaedic or spinal surgical education,employed wet or dry lab techniques,and assessed training effectiveness.Exclusion criteria consisted of non-English publications,abstracts only,non-orthopaedic research,and studies unrelated to simulation.Two reviewers independently screened titles,abstracts,and full texts,resolving discrepancies with a third reviewer.RESULTS From 1851 records,101 studies met inclusion:78 on dry labs,7 on wet labs,4 on both.Virtual reality(VR)simulations were most common,with AI increasingly used for feedback and assessment.Cadaveric training remains the gold standard for accuracy and tactile feedback,while dry labs-especially VR-offer scalability,lower cost(40%-60%savings in five studies),and accessibility for novices.Senior residents prefer wet labs for complex tasks;juniors favour dry labs for basics.Challenges include limited transferability data,lack of standard outcome metrics,and ethical concerns about cadaver use and AI assessment.CONCLUSION Wet and dry labs each have unique strengths in orthopaedic training.A hybrid approach combining both,supported by standardised assessments and outcome studies,is most effective.Future efforts should aim for uniform reporting,integrating new technologies,and policy support for hybrid curricula to enhance skills and patient care.展开更多
This study introduces a new ocean surface friction velocity scheme and a modified Thompson cloud microphysics parameterization scheme into the CMA-TYM model.The impact of these two parameterization schemes on the pred...This study introduces a new ocean surface friction velocity scheme and a modified Thompson cloud microphysics parameterization scheme into the CMA-TYM model.The impact of these two parameterization schemes on the prediction of the movement track and intensity of Typhoon Kompasu in 2021 is examined.Additionally,the possible reasons for their effects on tropical cyclone(TC)intensity prediction are analyzed.Statistical results show that both parameterization schemes improve the predictions of Typhoon Kompasu’s track and intensity.The influence on track prediction becomes evident after 60 h of model integration,while the significant positive impact on intensity prediction is observed after 66 h.Further analysis reveals that these two schemes affect the timing and magnitude of extreme TC intensity values by influencing the evolution of the TC’s warm-core structure.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
Analysis of the environmental and economic performance of fishing vessels has received limited attention compared with other ship types despite their notable contribution to global greenhouse gas(GHG)emissions.This st...Analysis of the environmental and economic performance of fishing vessels has received limited attention compared with other ship types despite their notable contribution to global greenhouse gas(GHG)emissions.This study evaluates the carbon footprint(CF)and economic viability of a liquefied natural gas(LNG)-fueled fishing vessel,using real engine operation simulations to provide precise and dynamic evaluation of fuel consumption and GHG emissions.Operational profiles are obtained through the utilization of onboard monitoring systems,whereas engine performance is simulated using the 1D/0D AVL Boost^(TM)model.Life cycle assessment(LCA)is conducted to quantify the environmental impact,whereas life cycle cost assessment(LCCA)is performed to analyze the profitability of LNG as an alternative fuel.The potential impact of the future fuel price uncertainties is addressed using Monte Carlo simulations.The LCA findings indicate that LNG has the potential to reduce the CF of the vessel by 14%to 16%,in comparison to a diesel power system configuration that serves as the baseline scenario.The LCCA results further indicate that the total cost of an LNG-powered ship is lower by 9.5%-13.8%,depending on the share of LNG and pilot fuels.This finding highlights the potential of LNG to produce considerable environmental benefits while addressing economic challenges under diverse operational and fuel price conditions.展开更多
One of the emerging applications of spouted beds is their utilization as thermal energy storage units in concentrated solar power systems(CSP).Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)is one of the...One of the emerging applications of spouted beds is their utilization as thermal energy storage units in concentrated solar power systems(CSP).Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)is one of the approaches to model multiphase flow reactors and gain insights into their behavior.Although several studies have used the CFD-DEM approach to investigate heat transfer in fluidized and spouted beds,research on CFD-DEM thermal modeling of spouted beds specifically as solar receivers in CSP systems remains limited.Therefore,the aim of this study is to evaluate the predictive capability of the CFD-DEM approach for modeling spouted bed thermal receivers and to gain insight into the hydrodynamic and thermal parameters that influence simulation results.An open-source program MFIX(Multiphase Flow with Interphase Exchanges)was used for model development.For model validation both cold and hot laboratory scale(15 cm cylindrical diameter,60°conical angle)conical spouted beds were built and used in experiments.CFD-DEM simulations were carried out for Carbo HSP particles(dp=0.95 mm,ρp=3630 kg/m^(3))at a static bed height of 100 mm.Throughout the study,the coarse-grained particle-DEM(CGP-DEM)method was used to reduce the computational time.The hydrodynamic simulation results indicate that gas-solid flow behavior in the spouted bed is well captured using both CGP-CFD-DEM and CFD-DEM approaches.The coarse-grained simulations of convective cooling during the discharge of a directly irradiated spouted bed with CarboHSP particles slightly underpredict the experimental cooling curve.Since the cooling curve is highly sensitive to wall boundary conditions,accurately determining these conditions is crucial for precise heat loss predictions.Furthermore,the coarse-grained particle diameter was found to have no significant effect on bed temperature.展开更多
Accurate prediction of apparent viscosity and analyzing the influence mechanism of particle behavior on apparent viscosity is of great importance for the semi-solid processing process.In this paper,the coupled CFD-DEM...Accurate prediction of apparent viscosity and analyzing the influence mechanism of particle behavior on apparent viscosity is of great importance for the semi-solid processing process.In this paper,the coupled CFD-DEM method is employed to study the solid-liquid two phase flow and particle behavior in semisolid aluminum.The artificial neural networks method is used to predict the lubrication force range and calculate the apparent viscosity of semi-solid aluminum.The results show that the increasing shear rate results in the increasing coordination number of clusters,indicating that the spherical evolution of clusters caused by shear is important reason for the shear thinning of semi-solid metal.The blockage caused by the large cluster formed under high solid volume fraction leads in the high apparent viscosity.Predicting the apparent viscosity of semi-solid metal must consider the particle agglomeration behavior.Based on artificial neural networks method,the apparent viscosity of semi-solid metal can be estimated accurately by predicting the lubrication force range under different solid volume fractions and shear conditions.展开更多
The coupled CFD-DEM simulations are widely recognized as a powerful approach for analyzing various particle-fluid systems.In lead-bismuth nuclear reactors,the liquid lead-bismuth eutectic(LBE)alloy is employed as the ...The coupled CFD-DEM simulations are widely recognized as a powerful approach for analyzing various particle-fluid systems.In lead-bismuth nuclear reactors,the liquid lead-bismuth eutectic(LBE)alloy is employed as the coolant,and the solid-phase oxygen control is a key technique for corrosion mitigation.In this work,diffusive smoothing CFD-DEM simulations are performed to investigate the particle-scale mass transfer behaviors of LBE solid-phase oxygen control loops.The dissolution of the lead oxide particle within the mass exchanger serves as the source term of the mass transfer processes.In the current model,the fluid flow,particle motion,particle-fluid interaction forces,and the mass transfer of oxygen concentration in LBE are incorporated in the governing equations.When the CFD cell size is smaller than the particle diameter,the diffusive smoothing method is proposed to calculate the void fraction field.Compared with the experimental results,the numerical simulations give a satisfactory prediction of the flow dynamics and particle-scale mass transfer.In the small-sized experiment,the total dissolution rate is about 0.0031 g/h at 380 C,and it is notably lower than the oxygen consumption in a full-scale megawatt-level lead-bismuth reactor.A large-scale mass exchanger is designed,and the numerical simulations indicate that the oxygen control system achieves a dissolution rate ranging from 5.28 to 23.74 g/h at temperatures of 380-420℃.It is sufficient to meet the expected oxygen consumption of 4.5 g/h in the nuclear reactor.The diffusive smoothing CFD-DEM approach provides a robust tool for the design and optimization of oxygen control loops of advanced lead-bismuth fast nuclear reactors.展开更多
The speed of sound waves in a fluidized bed is investigated using CFD-DEM numerical simulations, Appro- priate initial and boundary conditions are applied to reproduce bed phenomena. The effect of varying the height o...The speed of sound waves in a fluidized bed is investigated using CFD-DEM numerical simulations, Appro- priate initial and boundary conditions are applied to reproduce bed phenomena. The effect of varying the height of the bed is also studied. The results of the simulations matched those from the literature. The pressure and particle velocity profiles obtained feature oscillatory behavior to which functions （based on a damped standing wave） were fitted, enabling an explicit dependence on time and space variables to be established. These fitted functions were substituted into the linearized governing equations for the two-phase flow. These solutions enabled a new relationship to be derived for the speed of sound and damping in the system. The conclusion drawn is tbat the damping in the system is governed by the effective bulk viscosity of the solid phase, which arises from the particle viscosity.展开更多
Turbulent environment improves the flotation recovery of fine particles by promoting the particle–bubble collision rate,which directly depends on the particle slip velocity.However,the existing slip velocity models a...Turbulent environment improves the flotation recovery of fine particles by promoting the particle–bubble collision rate,which directly depends on the particle slip velocity.However,the existing slip velocity models are not applicable to fine particles in turbulence.The mechanism of turbulence characteristics and particle properties on the slip velocity of fine particles in turbulence was unclear.In this study,a coupled ANSYS FLUENT and EDEM based on computational fluid dynamics(CFD)and discrete element method(DEM)were used to simulate the slip velocity of fine particles in the approximately homogenous isotropic turbulence,which was excited by the grid.The reliability of the used CFD-DEM simulation method was validated against the slip velocity measured by the particle image velocimetry(PIV)experiments.In particular,the effects of the particle shapes,particle densities,and turbulence intensities on the slip velocity have been investigated with this numerical method.Numerical results show that particle shapes have no significant effect on fine particles between 37 and 225μm.The slip velocity of the spherical particles increases with the turbulence intensity and particle density.Based on the simulated data,a model which has a correlation coefficient of 0.95 is built by using nonlinear fitting.展开更多
Rovers on Mars and the Moon analyze the local geology by collecting samples of the upper layer in containers and ovens.After the analysis,the complete discharge of samples from the reservoir must be ensured.Because of...Rovers on Mars and the Moon analyze the local geology by collecting samples of the upper layer in containers and ovens.After the analysis,the complete discharge of samples from the reservoir must be ensured.Because of the low atmospheric pressure,reduced gravity,and different grain shapes of the bulk material,the discharge process is very different compared to that on Earth.In this study,the behavior of lunar regolith JSC-1A in closed containers during discharge was investigated by analyzing the flow in an hourglass under the Earth's atmosphere.Reproducible fluidization of the top particle layer was observed during the outflow of the upper half of the hourglass.These particles were fluidized by the displacement flow initiated by failing particles in the completely closed container.This complex problem was simulated by coupling computational fluid dynamics (CFD)with the discrete element method (DEM). A CFD-DEM simulation with 1million particles was performed.Because billions of particles are present in the actual system,the use of a coarse graining approach was required.In addition,high-speed camera measurements were used to determine the velocities of individual particles to validate the simulation. The fluidization effect was successfully simulated using the coupled method.展开更多
Particulate flows in a mixture of gas and liquid,i.e.gas-liquid-solid three-phase flows,are frequently encountered both in nature and industry.In such flows,complex interactions between multiple phases,i.e.particle-pa...Particulate flows in a mixture of gas and liquid,i.e.gas-liquid-solid three-phase flows,are frequently encountered both in nature and industry.In such flows,complex interactions between multiple phases,i.e.particle-particle interactions,fluid-particle interactions and interfacial interactions(such as surface tension and particle wetting),play a crucial role.In literature,simulations of three-phase flows are sometimes performed by incorporating interface capturing methods(e.g.VOF method)into the CFD-DEM coupling model.However,it is practically impossible to perform large(industrial)scale simulation because of the high computational cost.One of the strategies often employed to reduce the computational cost in CFD-DEM is to upscale particle size,which is applied mainly to particle single-phase and fluid-solid two-phase flows.The present work is focused on the scaled-up particle model for gas-liquid-solid three-phase flows.The interaction forces between multiple phases are scaled using the general criteria derived from the continuum assumption of particulate flow.A colour function based interface-capturing method with improved interface smoothness is developed,and the diffusion based coarse graining is employed to ensure sufficient space resolution in CFD even when particle size is increased.It is shown that the model developed is capable of predicting the both particles and fluid behaviour in the original system.展开更多
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.52274009)China Postdoctoral Science Foundation(Grant No.2022M723501)Science and Technology Planning Project of Sichuan Province(Grant No.2021YJ0359).
文摘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.
基金Rouven Weiler and Dominik Weis for their valuable insights,discussions,and feedback,which contributed to this work.We also gratefully acknowledge the financial support provided by BASF SE.
文摘Accurately predicting heat flux in coarse-grained CFD-DEM simulations is a significant challenge.Specifically,the rates of fluid-particle heat exchange,the effective thermal conductivity of a bed of particles,as well as radiative heat transfer rates are difficult to predict.By using a novel algorithm,we significantly improve the accuracy and stability of such simulations by using a heat exchange limiter.This limiter enables realistic predictions even at time steps that are three orders of magnitude larger than a typical fluid heat relaxation time.Additionally,view-factor-based corrections for radiative heat exchange computations are developed.These corrections ensure an effective thermal bed conductivity with less than 3%error for a coarse-graining ratio of 10.The applicability of the P1 radiation model in coarse-grained settings is also examined,leading to recommendations for the CFD grid resolution to ensure accurate predictions.Our methods significantly enhance stability,accuracy,and computational efficiency,making coarse-grained CFD-DEM simulations more viable for industrial applications.These advancements enable more reliable modeling of high-temperature processes,accelerate optimization studies,and enable virtual equipment design of such processes.
文摘BACKGROUND Orthopaedic surgical education has traditionally depended on the apprenticeship model of“see one,do one,teach one”.However,reduced operative exposure,stricter work-hour regulations,medicolegal constraints,and patient safety concerns have constrained its practicality.Simulation-based training has become a reliable,safe,and cost-efficient alternative.Dry lab techniques,especially virtual and augmented reality,make up 78%of current dry lab research,whereas wet labs still set the standard for anatomical realism.AIM To evaluate the effectiveness,limitations,and future directions of wet and dry lab simulation in orthopaedic training.METHODS A scoping review was carried out across four databases-PubMed,Cochrane Library,Web of Science,and EBSCOhost-up to 2025.Medical Subject Headings included:"Orthopaedic Education","Wet Lab","Dry Lab","Simulation Training","Virtual Reality",and"Surgical Procedure".Eligible studies focused on orthopaedic or spinal surgical education,employed wet or dry lab techniques,and assessed training effectiveness.Exclusion criteria consisted of non-English publications,abstracts only,non-orthopaedic research,and studies unrelated to simulation.Two reviewers independently screened titles,abstracts,and full texts,resolving discrepancies with a third reviewer.RESULTS From 1851 records,101 studies met inclusion:78 on dry labs,7 on wet labs,4 on both.Virtual reality(VR)simulations were most common,with AI increasingly used for feedback and assessment.Cadaveric training remains the gold standard for accuracy and tactile feedback,while dry labs-especially VR-offer scalability,lower cost(40%-60%savings in five studies),and accessibility for novices.Senior residents prefer wet labs for complex tasks;juniors favour dry labs for basics.Challenges include limited transferability data,lack of standard outcome metrics,and ethical concerns about cadaver use and AI assessment.CONCLUSION Wet and dry labs each have unique strengths in orthopaedic training.A hybrid approach combining both,supported by standardised assessments and outcome studies,is most effective.Future efforts should aim for uniform reporting,integrating new technologies,and policy support for hybrid curricula to enhance skills and patient care.
基金supported by the National Key R&D Program of China[grant number 2023YFC3008004]。
文摘This study introduces a new ocean surface friction velocity scheme and a modified Thompson cloud microphysics parameterization scheme into the CMA-TYM model.The impact of these two parameterization schemes on the prediction of the movement track and intensity of Typhoon Kompasu in 2021 is examined.Additionally,the possible reasons for their effects on tropical cyclone(TC)intensity prediction are analyzed.Statistical results show that both parameterization schemes improve the predictions of Typhoon Kompasu’s track and intensity.The influence on track prediction becomes evident after 60 h of model integration,while the significant positive impact on intensity prediction is observed after 66 h.Further analysis reveals that these two schemes affect the timing and magnitude of extreme TC intensity values by influencing the evolution of the TC’s warm-core structure.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
文摘Analysis of the environmental and economic performance of fishing vessels has received limited attention compared with other ship types despite their notable contribution to global greenhouse gas(GHG)emissions.This study evaluates the carbon footprint(CF)and economic viability of a liquefied natural gas(LNG)-fueled fishing vessel,using real engine operation simulations to provide precise and dynamic evaluation of fuel consumption and GHG emissions.Operational profiles are obtained through the utilization of onboard monitoring systems,whereas engine performance is simulated using the 1D/0D AVL Boost^(TM)model.Life cycle assessment(LCA)is conducted to quantify the environmental impact,whereas life cycle cost assessment(LCCA)is performed to analyze the profitability of LNG as an alternative fuel.The potential impact of the future fuel price uncertainties is addressed using Monte Carlo simulations.The LCA findings indicate that LNG has the potential to reduce the CF of the vessel by 14%to 16%,in comparison to a diesel power system configuration that serves as the baseline scenario.The LCCA results further indicate that the total cost of an LNG-powered ship is lower by 9.5%-13.8%,depending on the share of LNG and pilot fuels.This finding highlights the potential of LNG to produce considerable environmental benefits while addressing economic challenges under diverse operational and fuel price conditions.
基金was support of the Scientific and Technological Research Council of Turkey(Project No.MAG 122M514)。
文摘One of the emerging applications of spouted beds is their utilization as thermal energy storage units in concentrated solar power systems(CSP).Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)is one of the approaches to model multiphase flow reactors and gain insights into their behavior.Although several studies have used the CFD-DEM approach to investigate heat transfer in fluidized and spouted beds,research on CFD-DEM thermal modeling of spouted beds specifically as solar receivers in CSP systems remains limited.Therefore,the aim of this study is to evaluate the predictive capability of the CFD-DEM approach for modeling spouted bed thermal receivers and to gain insight into the hydrodynamic and thermal parameters that influence simulation results.An open-source program MFIX(Multiphase Flow with Interphase Exchanges)was used for model development.For model validation both cold and hot laboratory scale(15 cm cylindrical diameter,60°conical angle)conical spouted beds were built and used in experiments.CFD-DEM simulations were carried out for Carbo HSP particles(dp=0.95 mm,ρp=3630 kg/m^(3))at a static bed height of 100 mm.Throughout the study,the coarse-grained particle-DEM(CGP-DEM)method was used to reduce the computational time.The hydrodynamic simulation results indicate that gas-solid flow behavior in the spouted bed is well captured using both CGP-CFD-DEM and CFD-DEM approaches.The coarse-grained simulations of convective cooling during the discharge of a directly irradiated spouted bed with CarboHSP particles slightly underpredict the experimental cooling curve.Since the cooling curve is highly sensitive to wall boundary conditions,accurately determining these conditions is crucial for precise heat loss predictions.Furthermore,the coarse-grained particle diameter was found to have no significant effect on bed temperature.
基金supported by the Fundamental Research Funds for the Central Universities(grant No.N180904007)the open funds of Key Laboratory of Electromagnetic Processing of Materials,Ministry of Education,Northeastern University(grant No.NEUEPM-014)。
文摘Accurate prediction of apparent viscosity and analyzing the influence mechanism of particle behavior on apparent viscosity is of great importance for the semi-solid processing process.In this paper,the coupled CFD-DEM method is employed to study the solid-liquid two phase flow and particle behavior in semisolid aluminum.The artificial neural networks method is used to predict the lubrication force range and calculate the apparent viscosity of semi-solid aluminum.The results show that the increasing shear rate results in the increasing coordination number of clusters,indicating that the spherical evolution of clusters caused by shear is important reason for the shear thinning of semi-solid metal.The blockage caused by the large cluster formed under high solid volume fraction leads in the high apparent viscosity.Predicting the apparent viscosity of semi-solid metal must consider the particle agglomeration behavior.Based on artificial neural networks method,the apparent viscosity of semi-solid metal can be estimated accurately by predicting the lubrication force range under different solid volume fractions and shear conditions.
基金supported by the National Key R&D Program of China(grant No.2022YFB1902503)the National Natural Science Foundation of China(grant Nos.12027813,12105101)+1 种基金the Fund of Science and Technology on Reactor System Design Technology Laboratory(grant No.KFKT-05-FW-HT-20220010)the Fundamental Research Funds for the Central Universities.
文摘The coupled CFD-DEM simulations are widely recognized as a powerful approach for analyzing various particle-fluid systems.In lead-bismuth nuclear reactors,the liquid lead-bismuth eutectic(LBE)alloy is employed as the coolant,and the solid-phase oxygen control is a key technique for corrosion mitigation.In this work,diffusive smoothing CFD-DEM simulations are performed to investigate the particle-scale mass transfer behaviors of LBE solid-phase oxygen control loops.The dissolution of the lead oxide particle within the mass exchanger serves as the source term of the mass transfer processes.In the current model,the fluid flow,particle motion,particle-fluid interaction forces,and the mass transfer of oxygen concentration in LBE are incorporated in the governing equations.When the CFD cell size is smaller than the particle diameter,the diffusive smoothing method is proposed to calculate the void fraction field.Compared with the experimental results,the numerical simulations give a satisfactory prediction of the flow dynamics and particle-scale mass transfer.In the small-sized experiment,the total dissolution rate is about 0.0031 g/h at 380 C,and it is notably lower than the oxygen consumption in a full-scale megawatt-level lead-bismuth reactor.A large-scale mass exchanger is designed,and the numerical simulations indicate that the oxygen control system achieves a dissolution rate ranging from 5.28 to 23.74 g/h at temperatures of 380-420℃.It is sufficient to meet the expected oxygen consumption of 4.5 g/h in the nuclear reactor.The diffusive smoothing CFD-DEM approach provides a robust tool for the design and optimization of oxygen control loops of advanced lead-bismuth fast nuclear reactors.
文摘The speed of sound waves in a fluidized bed is investigated using CFD-DEM numerical simulations, Appro- priate initial and boundary conditions are applied to reproduce bed phenomena. The effect of varying the height of the bed is also studied. The results of the simulations matched those from the literature. The pressure and particle velocity profiles obtained feature oscillatory behavior to which functions （based on a damped standing wave） were fitted, enabling an explicit dependence on time and space variables to be established. These fitted functions were substituted into the linearized governing equations for the two-phase flow. These solutions enabled a new relationship to be derived for the speed of sound and damping in the system. The conclusion drawn is tbat the damping in the system is governed by the effective bulk viscosity of the solid phase, which arises from the particle viscosity.
基金This work was supported by National Natural Science Foundation of China(grant No.51974310,U21A20325).
文摘Turbulent environment improves the flotation recovery of fine particles by promoting the particle–bubble collision rate,which directly depends on the particle slip velocity.However,the existing slip velocity models are not applicable to fine particles in turbulence.The mechanism of turbulence characteristics and particle properties on the slip velocity of fine particles in turbulence was unclear.In this study,a coupled ANSYS FLUENT and EDEM based on computational fluid dynamics(CFD)and discrete element method(DEM)were used to simulate the slip velocity of fine particles in the approximately homogenous isotropic turbulence,which was excited by the grid.The reliability of the used CFD-DEM simulation method was validated against the slip velocity measured by the particle image velocimetry(PIV)experiments.In particular,the effects of the particle shapes,particle densities,and turbulence intensities on the slip velocity have been investigated with this numerical method.Numerical results show that particle shapes have no significant effect on fine particles between 37 and 225μm.The slip velocity of the spherical particles increases with the turbulence intensity and particle density.Based on the simulated data,a model which has a correlation coefficient of 0.95 is built by using nonlinear fitting.
文摘Rovers on Mars and the Moon analyze the local geology by collecting samples of the upper layer in containers and ovens.After the analysis,the complete discharge of samples from the reservoir must be ensured.Because of the low atmospheric pressure,reduced gravity,and different grain shapes of the bulk material,the discharge process is very different compared to that on Earth.In this study,the behavior of lunar regolith JSC-1A in closed containers during discharge was investigated by analyzing the flow in an hourglass under the Earth's atmosphere.Reproducible fluidization of the top particle layer was observed during the outflow of the upper half of the hourglass.These particles were fluidized by the displacement flow initiated by failing particles in the completely closed container.This complex problem was simulated by coupling computational fluid dynamics (CFD)with the discrete element method (DEM). A CFD-DEM simulation with 1million particles was performed.Because billions of particles are present in the actual system,the use of a coarse graining approach was required.In addition,high-speed camera measurements were used to determine the velocities of individual particles to validate the simulation. The fluidization effect was successfully simulated using the coupled method.
基金Procter&Gamble Technical Centers Ltd.,JSPS KAKENHI Grant No.18K13690the Information Center of Particle Technology,Japan for the financial support to this work.
文摘Particulate flows in a mixture of gas and liquid,i.e.gas-liquid-solid three-phase flows,are frequently encountered both in nature and industry.In such flows,complex interactions between multiple phases,i.e.particle-particle interactions,fluid-particle interactions and interfacial interactions(such as surface tension and particle wetting),play a crucial role.In literature,simulations of three-phase flows are sometimes performed by incorporating interface capturing methods(e.g.VOF method)into the CFD-DEM coupling model.However,it is practically impossible to perform large(industrial)scale simulation because of the high computational cost.One of the strategies often employed to reduce the computational cost in CFD-DEM is to upscale particle size,which is applied mainly to particle single-phase and fluid-solid two-phase flows.The present work is focused on the scaled-up particle model for gas-liquid-solid three-phase flows.The interaction forces between multiple phases are scaled using the general criteria derived from the continuum assumption of particulate flow.A colour function based interface-capturing method with improved interface smoothness is developed,and the diffusion based coarse graining is employed to ensure sufficient space resolution in CFD even when particle size is increased.It is shown that the model developed is capable of predicting the both particles and fluid behaviour in the original system.
