Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its format...Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradually. When the front of the melt reaches the end of the mold cavity, the front melt will backfill the mold; the wider the width of mold cavity, the better the mold filling ability. The mold filling ability of gallium melt in mold with upper magnetic conductor is better than that without upper magnetic conductor.展开更多
A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial ...A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial parameters determinate the cast microstructure,the one is electric-magnetic force(EMF)and the other is the frequency of AC current.Results show that the minor phase could be mixed in the other phase from the initial layered structure when the EMF above a specific value under fixed frequency,and the average diameter of minor phase droplet decreases with increasing EMF.The evolution of the liquid phases structure is reasonable agree with the realistic experiment of Zn-Bi hyper-monotectic alloy,which suggests that the mechanism revealed by the physical simulation could represent the one in the realistic experiment.展开更多
Physical simulation is used to study the movement of nonmetallic particles in Al melt in electro- magnetic field. It is found that the terminal velocity of particles in different Reynolds number range has different fu...Physical simulation is used to study the movement of nonmetallic particles in Al melt in electro- magnetic field. It is found that the terminal velocity of particles in different Reynolds number range has different functions. By confirming drag force coefficient of nonmetallic particles with Reynolds number in the range of 0.2-10 and 10-25 respectively, two functions of terminal ve- locity for spherical nonmetallic particles have been got accordingly, which provide a theoretical basis for separating nonmetallic inclusions from Al melt in electromagnetic field.展开更多
The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological ...The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological noise,there is still a significant gap between its actual precision and theoretical precision.This study identifies the key factor limiting the precision of the SERF gyroscope as coupling noise.By optimizing the detection loop structure,a distinction between the dual-axis signals'response to optical and magnetic fields was achieved-where the optical errors responded similarly,while the response to magnetic noise was opposite.Based on the differences in the optical-magnetic response of the dual-axis signals,empirical mode decomposition was used to decompose the dual-axis gyroscope signals into multiple intrinsic mode functions,and Allan deviation analysis was applied to analyze the noise characteristics of the intrinsic mode functions over various periods.This study successfully reveals that optical errors caused by thermal-optical coupling and long-period magnetic noise induced by thermal-magnetic coupling are the dominant factors limiting the long-term stability of the SERF gyroscope.Based on these analyses,the study concludes that to achieve strategic-grade precision for the SERF gyroscope,it is essential to effectively address the noise issues caused by multi-physical field couplings.展开更多
A 3-D numerical simulation with CFX software on physical field of multi-air channel coal burner in rotary kiln was carried out. The effects of various operational and structural parameters on flame feature and tempera...A 3-D numerical simulation with CFX software on physical field of multi-air channel coal burner in rotary kiln was carried out. The effects of various operational and structural parameters on flame feature and temperature distribution were investigated. A thermal measurement was conducted on a rotary kiln (4.5m in diameter, 90m in length) with four-air channel coal burner to determine the boundary conditions and to verify the simulation results. The calculation result shows that the distribution of velocity near burner exit is saddle-like; recirculation zones near nozzle and wall are useful for mixture primary air with coal and high temperature fume. A little central airflow can avoid coal backing up and cool nozzle. Adjusting the ratio of internal airflow to outer airflow is an effective and major means to regulate flame and temperature distribution in sintering region. Large whirlcone angle can intensify disturbution range at flame root to accelerate ignition and mixture. Large coal size can reduce high temperature region and result in coal combusting insufficiently. Too much combustion air will lengthen flame and increase heat loss.展开更多
An upwind finite element(FE)based algorithm to calculate the ion flow field in the vicinity of multi-circuit DC transmission lines is described.The initial value estimation and boundary condition are optimized,so deta...An upwind finite element(FE)based algorithm to calculate the ion flow field in the vicinity of multi-circuit DC transmission lines is described.The initial value estimation and boundary condition are optimized,so details of the transmission lines such as bundle conductors and ground wires can be taken into account in the simulation model.Comparison between measured and computed ground level total electrical field and ion current density shows satisfactory agreement.The ion flow field of a ±500 kV HVDC project with bipolar lines on the same tower is simulated.The total electrical field and ion current density on ground level are compared among different line arrangements.展开更多
To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure p...To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.展开更多
Most existing force feedback methods are still difficult to meet the requirements of real-time force calculation in virtual assembly and operation with complex objects. In addition, there is often an assumption that t...Most existing force feedback methods are still difficult to meet the requirements of real-time force calculation in virtual assembly and operation with complex objects. In addition, there is often an assumption that the controlled objects are completely flee and the target object is only completely fixed or flee, thus, the dynamics of the kinematic chain where the controlled objects are located are neglected during the physical simulation of the product manipulation with force feedback interaction. This paper proposes a physical simulation method of product assembly and operation manipulation based on statistically learned contact force prediction model and the coupling of force feedback and dynamics. In the proposed method, based on hidden Markov model （HMM） and local weighting learning （LWL）, contact force prediction model is constructed, which can estimate the contact force in real time during interaction. Based on computational load balance model, the computing resources are dynamically assigned and the dynamics integral step is optimized. In addition, smoothing process is performed to the force feedback on the synchronization points. Consequently, we can solve the coupling and synchronization problems of high-frequency feedback force servo. low-frequency dynamics solver servo and scene rendering servo, and realize highly stable and accurate force feedback in the physical simulation of product assembly and operation manipulation. This research proposes a physical simulation method of product assembly and operation manipulation.展开更多
This paper posits that we are living in a computer simulation to simulate physical reality which has the same computer simulation process as virtual reality (computer-simulated reality). The computer simulation proces...This paper posits that we are living in a computer simulation to simulate physical reality which has the same computer simulation process as virtual reality (computer-simulated reality). The computer simulation process involves the digital representation of data, the mathematical computation of the digitized data in geometric formation and transformation in space-time, and the selective retention of events in a narrative. Conventional physics cannot explain physical reality clearly, while computer-simulated physics can explain physical reality clearly by using the computer simulation process consisting of the digital representation component, the mathematical computation component, and the selective retention component. For the digital representation component, the three intrinsic data (properties) are rest mass-kinetic energy, electric charge, and spin which are represented by the digital space structure, the digital spin, and the digital electric charge, respectively. The digital representations of rest mass and kinetic energy are 1 as attachment space for the space of matter and 0 as detachment space for the zero-space of matter, respectively, to explain the Higgs field, the reverse Higgs field, quantum mechanics, special relativity, force fields, dark matter, and baryonic matter. The digital representations of the exclusive and the inclusive occupations of positions are 1/2 spin fermion and integer spin boson, respectively, to explain spatial translation by supersymmetry transformation and dark energy. The digital representations of the allowance and the disallowance of irreversible kinetic energy are integral electric charges and fractional electric charges, respectively, to explain the confinements of quarks and quasiparticles. For the mathematical computation component, the mathematical computation involves the reversible multiverse and oscillating M-theory as oscillating membrane-string-particle whose space-time dimension (D) number oscillates between 11D and 10D and between 10D and 4D to explain cosmology. For the selective retention component, gravity, the strong force, electromagnetism, and the weak force are the retained events during the reversible four-stage evolution of our universe, and are unified by the common narrative of the evolution.展开更多
With the rudder angles getting larger and larger,the moment and force on propeller shafts,which are caused by complex flowing field,become more and more.They influence the shafting alignment greatly.Stress analysis of...With the rudder angles getting larger and larger,the moment and force on propeller shafts,which are caused by complex flowing field,become more and more.They influence the shafting alignment greatly.Stress analysis of propeller shafts has been done under increasing rudder corner conditions with complex hydrodynamics simulation for a great domestic liquified natural gas(LNG) vessel,which is with dual propulsion systems.The improved three-moment equation is adopted in the process of dual propulsive shafting alignment.The calculated results show that the propeller hydrodynamic characteristics,which affect dual propulsive shafting alignment greatly,must be considered under large rudder angle conditions.Shafting accidents of Korean LNG vessels are interpreted reasonably.At the same time,salutary lessons and references are afforded to the marine multi-propulsion shafting alignment in the future.展开更多
<div style="text-align:justify;"> Rainfall infiltration is a porous medium flow problem with variable saturation. Based on the theoretical analysis of the flow field, electrical conductivity of rocks, ...<div style="text-align:justify;"> Rainfall infiltration is a porous medium flow problem with variable saturation. Based on the theoretical analysis of the flow field, electrical conductivity of rocks, the electrical field, the paper simulates the coupling relationship between the water saturation in soil and the apparent resistivity distribution. It combines the Richards equation, the Archie formula and the Laplace equation. The experiment simulates the potential field data by the Wenner setting in electrical exploration on a two-layer geologic model with continuous rainfall during 5 days, which shows that the effective saturation in soil is increasing with the rainfall time, while the apparent resistivity is decreasing. This can provide a theoretical basis for the analyzing the rainfall infiltration and porosity of the soil by using high-density electrical method in the future. </div>展开更多
The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace.A numerical model for the electromagnetic-thermal-hydrodynamic coupling...The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace.A numerical model for the electromagnetic-thermal-hydrodynamic coupling fields have been developed by using the finite element method(FEM)and a 2D numerical simulation for electromagnetic、 temperature and velocity fields of metallurgical-grade silicon melting in vacuum induction furnace were performed with a software Multi-physics Comsol 3.5a in this paper.The results showed that the temperature field was dependent observably on input power of coils and induction heating times and the maximum temperature gradient in melting pool was 215K in holding time.With the silicon molted gradually a clockwise vortex was come into being for electromagnetic stirring in the smelting poor.The variation of velocity field in melting silicon is mainly influenced with the change of the current intensity and power frequency.The numerical predications of temperature distribution are in good agreement with experiments.展开更多
文摘Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradually. When the front of the melt reaches the end of the mold cavity, the front melt will backfill the mold; the wider the width of mold cavity, the better the mold filling ability. The mold filling ability of gallium melt in mold with upper magnetic conductor is better than that without upper magnetic conductor.
基金Item Sponsored by National Science Foundation of China (No.50974085) National High-tech R&D Program of China (No.2009AA03Z109) +3 种基金Key Project from Science and Technology Commission of Shanghai Municipality (No.09dz1206401No.08dj 1400404 and No.08DZ1130100) Development Foundation for Talents in Shanghai (No.2009046) Specialized Research Fund for Doctoral Program of Higher Education (No.20093108110012)
文摘A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial parameters determinate the cast microstructure,the one is electric-magnetic force(EMF)and the other is the frequency of AC current.Results show that the minor phase could be mixed in the other phase from the initial layered structure when the EMF above a specific value under fixed frequency,and the average diameter of minor phase droplet decreases with increasing EMF.The evolution of the liquid phases structure is reasonable agree with the realistic experiment of Zn-Bi hyper-monotectic alloy,which suggests that the mechanism revealed by the physical simulation could represent the one in the realistic experiment.
基金supported by the National Natural Science Foundation of China(No.59871029)the China Postdoctoral Science Foundation.
文摘Physical simulation is used to study the movement of nonmetallic particles in Al melt in electro- magnetic field. It is found that the terminal velocity of particles in different Reynolds number range has different functions. By confirming drag force coefficient of nonmetallic particles with Reynolds number in the range of 0.2-10 and 10-25 respectively, two functions of terminal ve- locity for spherical nonmetallic particles have been got accordingly, which provide a theoretical basis for separating nonmetallic inclusions from Al melt in electromagnetic field.
基金supported by Hefei National Laboratory,Innovation Program for Quantum Science and Technology(2021ZD0300400/2021ZD0300402)the Beijing Natural Science Foundation(3252013)the China Postdoctoral Science Foundation(2024T171116).
文摘The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological noise,there is still a significant gap between its actual precision and theoretical precision.This study identifies the key factor limiting the precision of the SERF gyroscope as coupling noise.By optimizing the detection loop structure,a distinction between the dual-axis signals'response to optical and magnetic fields was achieved-where the optical errors responded similarly,while the response to magnetic noise was opposite.Based on the differences in the optical-magnetic response of the dual-axis signals,empirical mode decomposition was used to decompose the dual-axis gyroscope signals into multiple intrinsic mode functions,and Allan deviation analysis was applied to analyze the noise characteristics of the intrinsic mode functions over various periods.This study successfully reveals that optical errors caused by thermal-optical coupling and long-period magnetic noise induced by thermal-magnetic coupling are the dominant factors limiting the long-term stability of the SERF gyroscope.Based on these analyses,the study concludes that to achieve strategic-grade precision for the SERF gyroscope,it is essential to effectively address the noise issues caused by multi-physical field couplings.
文摘A 3-D numerical simulation with CFX software on physical field of multi-air channel coal burner in rotary kiln was carried out. The effects of various operational and structural parameters on flame feature and temperature distribution were investigated. A thermal measurement was conducted on a rotary kiln (4.5m in diameter, 90m in length) with four-air channel coal burner to determine the boundary conditions and to verify the simulation results. The calculation result shows that the distribution of velocity near burner exit is saddle-like; recirculation zones near nozzle and wall are useful for mixture primary air with coal and high temperature fume. A little central airflow can avoid coal backing up and cool nozzle. Adjusting the ratio of internal airflow to outer airflow is an effective and major means to regulate flame and temperature distribution in sintering region. Large whirlcone angle can intensify disturbution range at flame root to accelerate ignition and mixture. Large coal size can reduce high temperature region and result in coal combusting insufficiently. Too much combustion air will lengthen flame and increase heat loss.
基金Project Supported by China11th Five-year National Key Technologies R&D Program(2006BAA02A20)
文摘An upwind finite element(FE)based algorithm to calculate the ion flow field in the vicinity of multi-circuit DC transmission lines is described.The initial value estimation and boundary condition are optimized,so details of the transmission lines such as bundle conductors and ground wires can be taken into account in the simulation model.Comparison between measured and computed ground level total electrical field and ion current density shows satisfactory agreement.The ion flow field of a ±500 kV HVDC project with bipolar lines on the same tower is simulated.The total electrical field and ion current density on ground level are compared among different line arrangements.
基金Projects(51104187,51274241,61321003) supported by the National Natural Science Foundation of ChinaProject(20100162120008) supported by Doctoral Fund of Ministry of Education of China
文摘To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.
基金Supported by National Natural Science Foundation of China(51475418)National Basic Research 973 Program of China(2011CB706503)Science Fund for Creative Research Groups of National Natural Science Foundation of China(51221004)
文摘Most existing force feedback methods are still difficult to meet the requirements of real-time force calculation in virtual assembly and operation with complex objects. In addition, there is often an assumption that the controlled objects are completely flee and the target object is only completely fixed or flee, thus, the dynamics of the kinematic chain where the controlled objects are located are neglected during the physical simulation of the product manipulation with force feedback interaction. This paper proposes a physical simulation method of product assembly and operation manipulation based on statistically learned contact force prediction model and the coupling of force feedback and dynamics. In the proposed method, based on hidden Markov model （HMM） and local weighting learning （LWL）, contact force prediction model is constructed, which can estimate the contact force in real time during interaction. Based on computational load balance model, the computing resources are dynamically assigned and the dynamics integral step is optimized. In addition, smoothing process is performed to the force feedback on the synchronization points. Consequently, we can solve the coupling and synchronization problems of high-frequency feedback force servo. low-frequency dynamics solver servo and scene rendering servo, and realize highly stable and accurate force feedback in the physical simulation of product assembly and operation manipulation. This research proposes a physical simulation method of product assembly and operation manipulation.
文摘This paper posits that we are living in a computer simulation to simulate physical reality which has the same computer simulation process as virtual reality (computer-simulated reality). The computer simulation process involves the digital representation of data, the mathematical computation of the digitized data in geometric formation and transformation in space-time, and the selective retention of events in a narrative. Conventional physics cannot explain physical reality clearly, while computer-simulated physics can explain physical reality clearly by using the computer simulation process consisting of the digital representation component, the mathematical computation component, and the selective retention component. For the digital representation component, the three intrinsic data (properties) are rest mass-kinetic energy, electric charge, and spin which are represented by the digital space structure, the digital spin, and the digital electric charge, respectively. The digital representations of rest mass and kinetic energy are 1 as attachment space for the space of matter and 0 as detachment space for the zero-space of matter, respectively, to explain the Higgs field, the reverse Higgs field, quantum mechanics, special relativity, force fields, dark matter, and baryonic matter. The digital representations of the exclusive and the inclusive occupations of positions are 1/2 spin fermion and integer spin boson, respectively, to explain spatial translation by supersymmetry transformation and dark energy. The digital representations of the allowance and the disallowance of irreversible kinetic energy are integral electric charges and fractional electric charges, respectively, to explain the confinements of quarks and quasiparticles. For the mathematical computation component, the mathematical computation involves the reversible multiverse and oscillating M-theory as oscillating membrane-string-particle whose space-time dimension (D) number oscillates between 11D and 10D and between 10D and 4D to explain cosmology. For the selective retention component, gravity, the strong force, electromagnetism, and the weak force are the retained events during the reversible four-stage evolution of our universe, and are unified by the common narrative of the evolution.
基金the National Natural Science Foundation of China (Nos.50979058 and 51109131)the Simulation and Research Fund of Vessel Reducing Vibration with Stochastic Vibration Influence(No.J10LG60)
文摘With the rudder angles getting larger and larger,the moment and force on propeller shafts,which are caused by complex flowing field,become more and more.They influence the shafting alignment greatly.Stress analysis of propeller shafts has been done under increasing rudder corner conditions with complex hydrodynamics simulation for a great domestic liquified natural gas(LNG) vessel,which is with dual propulsion systems.The improved three-moment equation is adopted in the process of dual propulsive shafting alignment.The calculated results show that the propeller hydrodynamic characteristics,which affect dual propulsive shafting alignment greatly,must be considered under large rudder angle conditions.Shafting accidents of Korean LNG vessels are interpreted reasonably.At the same time,salutary lessons and references are afforded to the marine multi-propulsion shafting alignment in the future.
文摘<div style="text-align:justify;"> Rainfall infiltration is a porous medium flow problem with variable saturation. Based on the theoretical analysis of the flow field, electrical conductivity of rocks, the electrical field, the paper simulates the coupling relationship between the water saturation in soil and the apparent resistivity distribution. It combines the Richards equation, the Archie formula and the Laplace equation. The experiment simulates the potential field data by the Wenner setting in electrical exploration on a two-layer geologic model with continuous rainfall during 5 days, which shows that the effective saturation in soil is increasing with the rainfall time, while the apparent resistivity is decreasing. This can provide a theoretical basis for the analyzing the rainfall infiltration and porosity of the soil by using high-density electrical method in the future. </div>
基金Item Sponsored by the NSFC project (51066003u1137601) +1 种基金National science & technology support plan project (2011BAE03B01) Scientific Research Foundation Project (2010Y408) of Yunnan Province Education Department
文摘The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace.A numerical model for the electromagnetic-thermal-hydrodynamic coupling fields have been developed by using the finite element method(FEM)and a 2D numerical simulation for electromagnetic、 temperature and velocity fields of metallurgical-grade silicon melting in vacuum induction furnace were performed with a software Multi-physics Comsol 3.5a in this paper.The results showed that the temperature field was dependent observably on input power of coils and induction heating times and the maximum temperature gradient in melting pool was 215K in holding time.With the silicon molted gradually a clockwise vortex was come into being for electromagnetic stirring in the smelting poor.The variation of velocity field in melting silicon is mainly influenced with the change of the current intensity and power frequency.The numerical predications of temperature distribution are in good agreement with experiments.
