Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing addit...Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.展开更多
This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite elem...This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.展开更多
We take the established inductively coupled plasma(ICP) wind tunnel as a research object to investigate the thermal protection system of re-entry vehicles. A 1.2-MW high power ICP wind tunnel is studied through numeri...We take the established inductively coupled plasma(ICP) wind tunnel as a research object to investigate the thermal protection system of re-entry vehicles. A 1.2-MW high power ICP wind tunnel is studied through numerical simulation and experimental validation. The distribution characteristics and interaction mechanism of the flow field and electromagnetic field of the ICP wind tunnel are investigated using the multi-field coupling method of flow, electromagnetic, chemical, and thermodynamic field. The accuracy of the numerical simulation is validated by comparing the experimental results with the simulation results. Thereafter, the wind tunnel pressure, air velocity, electron density, Joule heating rate, Lorentz force, and electric field intensity obtained using the simulation are analyzed and discussed. The results indicate that for the 1.2-MW ICP wind tunnel, the maximum values of temperature, pressure, electron number density, and other parameters are observed during coil heating. The influence of the radial Lorentz force on the momentum transfer is stronger than that of the axial Lorentz force. The electron number density at the central axis and the amplitude and position of the Joule heating rate are affected by the radial Lorentz force. Moreover, the plasma in the wind tunnel is constantly in the subsonic flow state, and a strong eddy flow is easily generated at the inlet of the wind tunnel.展开更多
Two full 3D steady mathematical models are developed by finite element method （FEM） to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the...Two full 3D steady mathematical models are developed by finite element method （FEM） to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the acquired electromagnetic force as source body forces in Navier-Stokes equations. Effects caused by the ferromagnetic shell, busbar system around, and open boundary problem as well as inside induced current were considered in terms of the magnetic field. Furthermore, a new modeling method is found to set up solid models and then mesh them entirely with so-called structuralized grids, namely hex-mesh. Examples of 75kA prebaked cell with two kinds of busbar arrangements are presented. Results agree with those disclosed in the literature and confirm that the coupled simulation is valid. It is also concluded that the usage of these models facilitates the consistent analysis of the electric field to magnetic field and then flow motion to the greater extent, local distributions of current density and magnetic flux density are very much dependent on the cell structure, the steel shell is a shield to reduce the magnetic field and flow pattern is two dimensional in the main body of the metal pad.展开更多
A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet dur...A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.展开更多
Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the inf...Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.展开更多
The electron heating characteristics of magnetic enhancement capacitively coupled argon plasmas in presence of both longitudinal and transverse uniform magnetic field have been explored through both theoretical and nu...The electron heating characteristics of magnetic enhancement capacitively coupled argon plasmas in presence of both longitudinal and transverse uniform magnetic field have been explored through both theoretical and numerical calculations.It is found that the longitudinal magnetic field can affect the heating by changing the level of the pressure heating along the longitudinal direction and that of the Ohmic heating along the direction which is perpendicular to both driving electric field and the applied transverse magnetic field,and a continuously increased longitudinal magnetic field can induce pressure heating to become dominant.Moreover,the electron temperature as well as proportion of some low energy electrons will increase if a small longitudinal magnetic field is introduced,which is attributed to the increased average electron energy.We believe that the research will provide guidance for optimizing the magnetic field configuration of some discharge systems having both transverse and longitudinal magnetic field.展开更多
This article investigates the near-field dynamics in a particle-laden round turbulent jet in a large-eddy simulation （LES）. A point-force two-way coupling model is adopted in the simulation to reveal the particle mo...This article investigates the near-field dynamics in a particle-laden round turbulent jet in a large-eddy simulation （LES）. A point-force two-way coupling model is adopted in the simulation to reveal the particle modulation of turbulence. The particles mainly excite the initial instability of the jet and bring about the earlier breakup of vortex rings in the near-field. The flow fluc- tuating intensity either in the axial or in the radial directions is hence increased by particles. The article also describes the mean velocity modulated by particles. The changing statistical velocity induced by particle modulation implies the effects of modulation of the local flow structures. This study is expected to be useful to the control of two-phase turbulent jets.展开更多
To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dime...To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.展开更多
The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field...The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.展开更多
Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a...Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a water conveyance channel in Jilin Province,northern China,and found after monitoring that the frost heave at the channel bottom lining exceeded that at the crest by 44.5 mm,with the freezing temperature at the bottom being over 2℃lower than that at the crest.Soil columns with an initial gravimetric moisture content of 12%,16%,18%,and 20%were then prepared.The effects of temperature and moisture content on frost heave were analyzed under two freezing conditions(-5℃and-10℃)through unidirectional freezing tests.A coupled thermo-hydro-mechanical(THM)frost heave model,validated by the test results,was further established.In the soil with an initial moisture content of 20%,the formation of ice lenses associated with substantial water migration contributed to a large temperature gradient,which can jointly induce frost heave.Under the-10℃condition,the temperature gradient in the soil column with a 20%initial moisture content reached 0.84℃/cm,the total water migration reached 10.72%,and the frost heave deformation was 1.86 mm.The THM coupling results indicated that,under the interaction of a large temperature gradient and moisture accumulation,the volumetric ice content remained high in the bottom soil during freezing and peaked at 0.36.The frost damage to the bottom soil was severe,and the maximum deformation reached 57 mm.展开更多
Conventional concentrator photovoltaics(CPV)face a persistent trade-off between high efficiency and high cost,driven by expensive multi-junction solar cells and complex active cooling systems.This study presents a com...Conventional concentrator photovoltaics(CPV)face a persistent trade-off between high efficiency and high cost,driven by expensive multi-junction solar cells and complex active cooling systems.This study presents a computational investigation of a novel Multi-Focal Pyramidal Array(MFPA)-based CPV system designed to overcome this limitation.The MFPA architecture employs a geometrically optimized pyramidal concentrator to distribute concen-trated sunlight onto strategically placed,low-cost monocrystalline silicon cells,enabling high efficiency energy capture while passively managing thermal loads.Coupled optical thermal electrical simulations in COMSOL Multiphysics demonstrate a geometric concentration ratio of 120×,with system temperatures maintained below 110℃ under standard 1000 W/m2 Direct Normal Irradiance(DNI).Ray tracing confirms 95%optical efficiency and a concentrated light spot radius of 2.48 mm.Compared with conventional CPV designs,the MFPA improves power-per-cost by 25%and reduces tracking requirements by 50%owing to its wide±15°acceptance angle.These results highlight the MFPA’s potential as a scalable,low-cost,and energy-efficient pathway for expanding solar power generation.展开更多
All-solid-state lithium metal batteries represent leading candidates for the next generation of highenergy-density rechargeable batteries.However,the coupled mechanisms governing dendrite growth and crack propagation ...All-solid-state lithium metal batteries represent leading candidates for the next generation of highenergy-density rechargeable batteries.However,the coupled mechanisms governing dendrite growth and crack propagation within solid-state electrolytes(SSEs)remain inadequately understood.To address this knowledge gap,we propose an electrochemical-mechanical coupled phase-field model designed to simulate the complex processes of lithium deposition and crack propagation in SSEs.This framework systematically examines the influence of initial defect characteristics—including morphology,dimensions,and fracture toughness—on dendrite penetration dynamics.Furthermore,it identifies potential initiation pathways for detrimental lithium deposition within the electrolyte bulk.The model also quantifies the critical role of electrolyte elastic modulus and grain boundary orientation in modulating deposition behavior.Notably,simulation results demonstrate concordance with existing experimental observations,thereby establishing a fundamental theoretical framework for understanding failure mechanisms.This work provides crucial mechanistic insights and predictive capabilities to guide the rational design of failure-resistant SSEs for all-solid-state lithium metal batteries.展开更多
Tofigure out the process and controlling factors of gas reservoir formation in deep-waters,based on an analysis of geological features,source of natural gas and process of reservoir formation in the Liwan 3-1 gasfield...Tofigure out the process and controlling factors of gas reservoir formation in deep-waters,based on an analysis of geological features,source of natural gas and process of reservoir formation in the Liwan 3-1 gasfield,physical simulation experiment of the gas reservoir formation process has been performed,consequently,pattern and features of gas reservoir formation in the Baiyun sag has been found out.The results of the experiment show that:①the formation of the Liwan 3-1 faulted anticline gasfield is closely related to the longstanding active large faults,where natural gas is composed of a high proportion of hydrocarbons,a small amount of non-hydrocarbons,and the wet gas generated during highly mature stage shows obvious vertical migration signs;②liquid hydrocarbons associated with natural gas there are derived from source rock of the Enping&Zhuhai Formation,whereas natural gas comes mainly from source rock of the Enping Formation,and source rock of the Wenchang Formation made a little contribution during the early Eocene period as well;③although there was gas migration and accumulation,yet most of the natural gas mainly scattered and dispersed due to the stronger activity of faults in the early period;later as fault activity gradually weakened,gas started to accumulate into reservoirs in the Baiyun sag;④there is stronger vertical migration of oil and gas than lateral migration,and the places where fault links effective source rocks with reservoirs are most likely for gas accumulation;⑤effective temporal-spatial coupling of source-fault-reservoir in late stage is the key to gas reservoir formation in the Baiyun sag;⑥the nearer the distance from a trap to a large-scale fault and hydrocarbon source kitchen,the more likely gas may accumulate in the trap in late stage,therefore gas accumulation efficiency is much lower for the traps which are far away from large-scale faults and hydrocarbon source kitchens.展开更多
In order to study the temperature distribution of deep field,mathematical mod- els of temperature field in field and surrounding rock were built based on heat transfer and seepage theory.Combined test data with mathem...In order to study the temperature distribution of deep field,mathematical mod- els of temperature field in field and surrounding rock were built based on heat transfer and seepage theory.Combined test data with mathematical model,the temperature distribution under heat-transfer and underground-water coupling was studied by using Golden Soft- ware Surfer and Matlab.The results show that distribution law of most isothermal lines is very similar in deep field,and temperature gradient is equal in general.At the same time, temperature distribution is influenced by underground-water and fault.In surrounding rock, seepage changes symmetrical distribution of temperature field and vector,and the tem- perature field may divide into inward-diffusion area and outward-diffusion area.Peripheral temperature of working will approach to the temperature of airflow.In inward diffusion area the distribution of temperature and temperature vector is symmetric,and the direction of temperature vector point to the center of working.The action of airflow is stronger than seepage in inward diffusion area,however,the case opposite is true in outward diffusion area.展开更多
This paper analyzes the sources of heat losses in magnetic fluid bearings,proposes various cou-pling relationships of physical fields,divides the coupled heat transfer surfaces while ensuring the continuity of heat fl...This paper analyzes the sources of heat losses in magnetic fluid bearings,proposes various cou-pling relationships of physical fields,divides the coupled heat transfer surfaces while ensuring the continuity of heat flux density,and analyzes the overall heat dissipation pathways of the bearings.By changing parameters such as input current,rotor speed,and inlet oil flow rate,the study applies a multi-physics field coupling method to investigate the influence of different parameters on the temper-ature field and heat dissipation patterns of the bearings,which is then validated through experi-ments.This research provides a theoretical basis for the optimal design of magnetic fluid bearing sys-tems.展开更多
This study focuses on the distribution of high-resistance media(pores and spinels)within ZnO varistors and explores the mechanical and electrical failure mechanisms of varistors under different pulse actions.Micro-CT ...This study focuses on the distribution of high-resistance media(pores and spinels)within ZnO varistors and explores the mechanical and electrical failure mechanisms of varistors under different pulse actions.Micro-CT technology revealed that the proportion of high-resistance media in the edge area is much higher than in the internal area.Simulation results indicated that a high porosity significantly increased temperature rise and thermal stress concentration,while a high spinel proportion exacerbated current concentration but had a relatively minor impact on the distribution of temperature rise and thermal stress.Under an electric field of 1000-1250 V/mm,pores transition from an insulating state to a conductive state,especially in the edge area,leading to concentrated temperature rise and thermal stress.Once the thermal stress exceeded the critical value of the mechanical strength of the pores,cracking failure occurred.The high spinel proportion in the edge area further intensified current concentration under high electric fields,working together with the conductivity of the pores to produce a significant local temperature rise,melting grain structure,and ultimately leading to puncture failure.This study provides a new perspective for understanding the failure mechanism of ZnO varistors and lays a theoretical foundation for the development of varistor materials with high energy absorption capacity.展开更多
In this paper, the development status of casting numerical simulation technology is introduced. In additional, mathematical model, solution method, initial condition, boundary condition and defect predicting scheme of...In this paper, the development status of casting numerical simulation technology is introduced. In additional, mathematical model, solution method, initial condition, boundary condition and defect predicting scheme of foundry process are also analyzed, which include the mold filling process, solidification process and the process coupling fluid flow with heat transfer. Finally, a practical casting is taken out to show how to predict defects and optimize foundry process with numerical simulation technology.展开更多
Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the ...Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.展开更多
To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI) process has been optimized by simulation. A 2D axisymmetric unstable model was built, which ...To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI) process has been optimized by simulation. A 2D axisymmetric unstable model was built, which included convection, conduction, diffusion, densification reactions in the pores and the evolution of the porous medium. The multi-physical field coupling model was solved by finite element method (FEM) and iterative calculation. The time evolution of the fluid, temperature and preform density field were obtained by the calculation. It is indicated that convection strongly affects the temperature field. For the preform of carbon/carbon composites infiltrated for 100 h by TCVI, the radial average densities from simulation agrees well with those from experiment. The model is validated to be reliable and the simulation has capability of forecasting the process.展开更多
基金National Key Research and Development Program of China(2022YFB4600902)Shandong Provincial Science Foundation for Outstanding Young Scholars(ZR2024YQ020)。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.
基金supported by the National Natural Science Foundation of China (No. 50575205)the Hi-Tech Research and Development (863) Program of China (Nos. 2006AA04Z233 and 2007AA04Z101)+1 种基金the Doctoral Foundation of Ministry of Education of China (No. 20070335204)the Zhejiang Provincial Natural Science Foundation of China (No. Z1080537)
文摘This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.
基金supported by the National Natural Science Foundation of China (Grant No. 11705143)the Open Foundation for Key Laboratories of National Defense Science and Technology of China (Grant No. 6142202031901)the Foundation for Research and Development of Applied Technology in Beilin District of Xi’an,China (Grant No. GX2047)。
文摘We take the established inductively coupled plasma(ICP) wind tunnel as a research object to investigate the thermal protection system of re-entry vehicles. A 1.2-MW high power ICP wind tunnel is studied through numerical simulation and experimental validation. The distribution characteristics and interaction mechanism of the flow field and electromagnetic field of the ICP wind tunnel are investigated using the multi-field coupling method of flow, electromagnetic, chemical, and thermodynamic field. The accuracy of the numerical simulation is validated by comparing the experimental results with the simulation results. Thereafter, the wind tunnel pressure, air velocity, electron density, Joule heating rate, Lorentz force, and electric field intensity obtained using the simulation are analyzed and discussed. The results indicate that for the 1.2-MW ICP wind tunnel, the maximum values of temperature, pressure, electron number density, and other parameters are observed during coil heating. The influence of the radial Lorentz force on the momentum transfer is stronger than that of the axial Lorentz force. The electron number density at the central axis and the amplitude and position of the Joule heating rate are affected by the radial Lorentz force. Moreover, the plasma in the wind tunnel is constantly in the subsonic flow state, and a strong eddy flow is easily generated at the inlet of the wind tunnel.
基金the National High Technical Reasearch and Development Programme of China （No. 2003AA327140） the National Natural Science Foundation of China （No. 50374081）.
文摘Two full 3D steady mathematical models are developed by finite element method （FEM） to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the acquired electromagnetic force as source body forces in Navier-Stokes equations. Effects caused by the ferromagnetic shell, busbar system around, and open boundary problem as well as inside induced current were considered in terms of the magnetic field. Furthermore, a new modeling method is found to set up solid models and then mesh them entirely with so-called structuralized grids, namely hex-mesh. Examples of 75kA prebaked cell with two kinds of busbar arrangements are presented. Results agree with those disclosed in the literature and confirm that the coupled simulation is valid. It is also concluded that the usage of these models facilitates the consistent analysis of the electric field to magnetic field and then flow motion to the greater extent, local distributions of current density and magnetic flux density are very much dependent on the cell structure, the steel shell is a shield to reduce the magnetic field and flow pattern is two dimensional in the main body of the metal pad.
基金the National Natural Science Foundation of China(Nos.11932008 and 11672120)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2022-kb01)。
文摘A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.
文摘Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.
基金supported by National Natural Science Foundation of China (Nos. 11975163 and 12175160)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘The electron heating characteristics of magnetic enhancement capacitively coupled argon plasmas in presence of both longitudinal and transverse uniform magnetic field have been explored through both theoretical and numerical calculations.It is found that the longitudinal magnetic field can affect the heating by changing the level of the pressure heating along the longitudinal direction and that of the Ohmic heating along the direction which is perpendicular to both driving electric field and the applied transverse magnetic field,and a continuously increased longitudinal magnetic field can induce pressure heating to become dominant.Moreover,the electron temperature as well as proportion of some low energy electrons will increase if a small longitudinal magnetic field is introduced,which is attributed to the increased average electron energy.We believe that the research will provide guidance for optimizing the magnetic field configuration of some discharge systems having both transverse and longitudinal magnetic field.
基金National Natural Science Foundation of China (50706021)Ph.D.Programs Foundation of Ministry of Education of China (20070003018)TNList Cross-discipline Foundation
文摘This article investigates the near-field dynamics in a particle-laden round turbulent jet in a large-eddy simulation （LES）. A point-force two-way coupling model is adopted in the simulation to reveal the particle modulation of turbulence. The particles mainly excite the initial instability of the jet and bring about the earlier breakup of vortex rings in the near-field. The flow fluc- tuating intensity either in the axial or in the radial directions is hence increased by particles. The article also describes the mean velocity modulated by particles. The changing statistical velocity induced by particle modulation implies the effects of modulation of the local flow structures. This study is expected to be useful to the control of two-phase turbulent jets.
文摘To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.
文摘The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.
基金funding support from the National Natural Science Foundation of China(Grants Nos.42330708 and 42302329)the Graduate Innovation Research Program of Jilin University(Grant No.2024CX118).
文摘Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a water conveyance channel in Jilin Province,northern China,and found after monitoring that the frost heave at the channel bottom lining exceeded that at the crest by 44.5 mm,with the freezing temperature at the bottom being over 2℃lower than that at the crest.Soil columns with an initial gravimetric moisture content of 12%,16%,18%,and 20%were then prepared.The effects of temperature and moisture content on frost heave were analyzed under two freezing conditions(-5℃and-10℃)through unidirectional freezing tests.A coupled thermo-hydro-mechanical(THM)frost heave model,validated by the test results,was further established.In the soil with an initial moisture content of 20%,the formation of ice lenses associated with substantial water migration contributed to a large temperature gradient,which can jointly induce frost heave.Under the-10℃condition,the temperature gradient in the soil column with a 20%initial moisture content reached 0.84℃/cm,the total water migration reached 10.72%,and the frost heave deformation was 1.86 mm.The THM coupling results indicated that,under the interaction of a large temperature gradient and moisture accumulation,the volumetric ice content remained high in the bottom soil during freezing and peaked at 0.36.The frost damage to the bottom soil was severe,and the maximum deformation reached 57 mm.
文摘Conventional concentrator photovoltaics(CPV)face a persistent trade-off between high efficiency and high cost,driven by expensive multi-junction solar cells and complex active cooling systems.This study presents a computational investigation of a novel Multi-Focal Pyramidal Array(MFPA)-based CPV system designed to overcome this limitation.The MFPA architecture employs a geometrically optimized pyramidal concentrator to distribute concen-trated sunlight onto strategically placed,low-cost monocrystalline silicon cells,enabling high efficiency energy capture while passively managing thermal loads.Coupled optical thermal electrical simulations in COMSOL Multiphysics demonstrate a geometric concentration ratio of 120×,with system temperatures maintained below 110℃ under standard 1000 W/m2 Direct Normal Irradiance(DNI).Ray tracing confirms 95%optical efficiency and a concentrated light spot radius of 2.48 mm.Compared with conventional CPV designs,the MFPA improves power-per-cost by 25%and reduces tracking requirements by 50%owing to its wide±15°acceptance angle.These results highlight the MFPA’s potential as a scalable,low-cost,and energy-efficient pathway for expanding solar power generation.
基金supported by the National Natural Science Foundation of China(No.52476053,No.22409209)Beijing Natural Science Foundation(No.3242017)。
文摘All-solid-state lithium metal batteries represent leading candidates for the next generation of highenergy-density rechargeable batteries.However,the coupled mechanisms governing dendrite growth and crack propagation within solid-state electrolytes(SSEs)remain inadequately understood.To address this knowledge gap,we propose an electrochemical-mechanical coupled phase-field model designed to simulate the complex processes of lithium deposition and crack propagation in SSEs.This framework systematically examines the influence of initial defect characteristics—including morphology,dimensions,and fracture toughness—on dendrite penetration dynamics.Furthermore,it identifies potential initiation pathways for detrimental lithium deposition within the electrolyte bulk.The model also quantifies the critical role of electrolyte elastic modulus and grain boundary orientation in modulating deposition behavior.Notably,simulation results demonstrate concordance with existing experimental observations,thereby establishing a fundamental theoretical framework for understanding failure mechanisms.This work provides crucial mechanistic insights and predictive capabilities to guide the rational design of failure-resistant SSEs for all-solid-state lithium metal batteries.
基金National High Technology Research and Development Program of China“Fundamental Study on Formation and Distribution of Hydrocarbon Resources in Deep-water Basins,South China Sea”(No.2009CB219400).
文摘Tofigure out the process and controlling factors of gas reservoir formation in deep-waters,based on an analysis of geological features,source of natural gas and process of reservoir formation in the Liwan 3-1 gasfield,physical simulation experiment of the gas reservoir formation process has been performed,consequently,pattern and features of gas reservoir formation in the Baiyun sag has been found out.The results of the experiment show that:①the formation of the Liwan 3-1 faulted anticline gasfield is closely related to the longstanding active large faults,where natural gas is composed of a high proportion of hydrocarbons,a small amount of non-hydrocarbons,and the wet gas generated during highly mature stage shows obvious vertical migration signs;②liquid hydrocarbons associated with natural gas there are derived from source rock of the Enping&Zhuhai Formation,whereas natural gas comes mainly from source rock of the Enping Formation,and source rock of the Wenchang Formation made a little contribution during the early Eocene period as well;③although there was gas migration and accumulation,yet most of the natural gas mainly scattered and dispersed due to the stronger activity of faults in the early period;later as fault activity gradually weakened,gas started to accumulate into reservoirs in the Baiyun sag;④there is stronger vertical migration of oil and gas than lateral migration,and the places where fault links effective source rocks with reservoirs are most likely for gas accumulation;⑤effective temporal-spatial coupling of source-fault-reservoir in late stage is the key to gas reservoir formation in the Baiyun sag;⑥the nearer the distance from a trap to a large-scale fault and hydrocarbon source kitchen,the more likely gas may accumulate in the trap in late stage,therefore gas accumulation efficiency is much lower for the traps which are far away from large-scale faults and hydrocarbon source kitchens.
基金Foundation of Liaoning Educational Committee(2007F049,20060390)
文摘In order to study the temperature distribution of deep field,mathematical mod- els of temperature field in field and surrounding rock were built based on heat transfer and seepage theory.Combined test data with mathematical model,the temperature distribution under heat-transfer and underground-water coupling was studied by using Golden Soft- ware Surfer and Matlab.The results show that distribution law of most isothermal lines is very similar in deep field,and temperature gradient is equal in general.At the same time, temperature distribution is influenced by underground-water and fault.In surrounding rock, seepage changes symmetrical distribution of temperature field and vector,and the tem- perature field may divide into inward-diffusion area and outward-diffusion area.Peripheral temperature of working will approach to the temperature of airflow.In inward diffusion area the distribution of temperature and temperature vector is symmetric,and the direction of temperature vector point to the center of working.The action of airflow is stronger than seepage in inward diffusion area,however,the case opposite is true in outward diffusion area.
基金the National Natural Science Foundation of China(No.52075468)the Natural Science Foundation of Hebei Province(No.E2020203052)+1 种基金the Key Scientific Research Projects of North China University of Technology(No.ZD-YG-202306-23)the Tangshan Science and Technology Project(No.23130201E).
文摘This paper analyzes the sources of heat losses in magnetic fluid bearings,proposes various cou-pling relationships of physical fields,divides the coupled heat transfer surfaces while ensuring the continuity of heat flux density,and analyzes the overall heat dissipation pathways of the bearings.By changing parameters such as input current,rotor speed,and inlet oil flow rate,the study applies a multi-physics field coupling method to investigate the influence of different parameters on the temper-ature field and heat dissipation patterns of the bearings,which is then validated through experi-ments.This research provides a theoretical basis for the optimal design of magnetic fluid bearing sys-tems.
基金National Natural Science Foundation of China(Youth Fund Program),Grant/Award Number:52107158Natural Science Foundation of Sichuan Province,Grant/Award Number:2024NSFSC0116Project of‘Gathering Resources to Prosper Sichuan’,Grant/Award Number:25JYXC0046。
文摘This study focuses on the distribution of high-resistance media(pores and spinels)within ZnO varistors and explores the mechanical and electrical failure mechanisms of varistors under different pulse actions.Micro-CT technology revealed that the proportion of high-resistance media in the edge area is much higher than in the internal area.Simulation results indicated that a high porosity significantly increased temperature rise and thermal stress concentration,while a high spinel proportion exacerbated current concentration but had a relatively minor impact on the distribution of temperature rise and thermal stress.Under an electric field of 1000-1250 V/mm,pores transition from an insulating state to a conductive state,especially in the edge area,leading to concentrated temperature rise and thermal stress.Once the thermal stress exceeded the critical value of the mechanical strength of the pores,cracking failure occurred.The high spinel proportion in the edge area further intensified current concentration under high electric fields,working together with the conductivity of the pores to produce a significant local temperature rise,melting grain structure,and ultimately leading to puncture failure.This study provides a new perspective for understanding the failure mechanism of ZnO varistors and lays a theoretical foundation for the development of varistor materials with high energy absorption capacity.
文摘In this paper, the development status of casting numerical simulation technology is introduced. In additional, mathematical model, solution method, initial condition, boundary condition and defect predicting scheme of foundry process are also analyzed, which include the mold filling process, solidification process and the process coupling fluid flow with heat transfer. Finally, a practical casting is taken out to show how to predict defects and optimize foundry process with numerical simulation technology.
基金supported by National Key Research Development Planning Project of China (2004CB619108).
文摘Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.
基金Supported by the National Natural Science Foundation of China (Grant No. 90716024)
文摘To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI) process has been optimized by simulation. A 2D axisymmetric unstable model was built, which included convection, conduction, diffusion, densification reactions in the pores and the evolution of the porous medium. The multi-physical field coupling model was solved by finite element method (FEM) and iterative calculation. The time evolution of the fluid, temperature and preform density field were obtained by the calculation. It is indicated that convection strongly affects the temperature field. For the preform of carbon/carbon composites infiltrated for 100 h by TCVI, the radial average densities from simulation agrees well with those from experiment. The model is validated to be reliable and the simulation has capability of forecasting the process.
