The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including...The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850＋ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth＇s deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the northcomponent azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.展开更多
The vortex pump is suitable for salt solution transportation. But the salt-out flow mechanism in the pump has not been understood fully. Salt-out layer formation and growth rate are closely related to crystal particle...The vortex pump is suitable for salt solution transportation. But the salt-out flow mechanism in the pump has not been understood fully. Salt-out layer formation and growth rate are closely related to crystal particle motion and concentration distribution. Study on the particle hydrodynamic characteristics in the pump volute becomes a key problem, because the crystal particles are mainly distributing in this zone after they enter the pump. Phase Doppler particle analyzer（PDPA） is used to measure the two-phase flow field in a model pump volute to get more understanding about the salt-out phenomenon. The crystal particle velocities are obtained in all three peripheral, radial and axial directions. Particle size and particle number density（PND） measurements are also performed in the experiment. Results are presented and discussed along the radial direction under different pump operating conditions, as well as various axial measurement positions. It is found that particle velocity gradient of peripheral component varies with the pump discharge. There is a turning point of relation between peripheral velocity component and discharge. Radial flow velocity curves look like a saddle shape and velocity magnitudes are changing greatly with the discharge. The non-equilibrium velocity feature between liquid and solid phase on this direction is also remarkable. Particles flow into the impeller at radial position R〈I, and the axial velocity component increases in this region. The particle size curve shows an open-up parabola distribution. The largest particles are distributing near the casing peripheral wall. As flow rate increases, accordingly PND increases. It also grows up in the axial-outward direction towards the suction cover. Crystal particle aggregation phenomenon can be revealed from the analysis of particle size and PND distribution, and the aggregation region is determined as well. Research results are helpful for optimal design of this kind of pump preventing salt-out.展开更多
The particle motion behavior affects the distribution of particles in the metal matrix and finally determines the mechanical properties of the particle reinforced metal-matrix composites. To obtain a uniform distribut...The particle motion behavior affects the distribution of particles in the metal matrix and finally determines the mechanical properties of the particle reinforced metal-matrix composites. To obtain a uniform distribution of TiC particles and excellent strengthening effect in 20%TiC/ZG270-500 composites fabricated by lost foam-squeeze casting （LFSC）, the particle motion behavior in the gas gap and the conditions of the particles getting into the molten steel were investigated. The results show that the airflow velocity （vl） and TiC particle motion velocity （up） change little with the pouring temperature （Tp）, increase with an increase in metal filling velocity （Vp）, ratios of cross sections of in-gate/orifice （AAAo） and orifice/mould cavity （AolAI）, but the increase trend of up is more intense. The airflow pressure （P1） changes little with Tp and Ao/A1, but increases with the increasing of vp and AJAo. Besides, there is a critical velocity （v ＋｜3YLG cosθ/ppdp｜1/2）for the particles getting into the molten steel. The higher the particle motion velocity, the easier the particles get into the molten steel and the more uniform the distribution of the particles in the steel matrix. When Tp = 1,873 K, vp = 30 mm.s-1, AJAo =10 and Ao/AI = 0.02 in this study, the biggest TiC particle motion velocity （20.59 m.s-~） can be gained, and the steel matrix with the most uniformly distributed TiC particles and fine grains are obtained.展开更多
Fluid particles in translating surface gravity waves have an orbital motion which decreases in size with increasing mean depth. These wave characteristics came from observations and were not forecast theoretically. Th...Fluid particles in translating surface gravity waves have an orbital motion which decreases in size with increasing mean depth. These wave characteristics came from observations and were not forecast theoretically. The classical potential flow model is incapable of explaining the particle movement due to the irrotational assumption and to a flaw in carrying out the method. When a wave passes by an observer from left to right, the particles move clockwise under a crest and a trough. This correct conclusion is consistent with what the incorrect standard theory implies but should not be considered to have been derived from it.展开更多
A new mathematical model, fluctuation spectrum random trajectory model (FSRTM) for the particle motion in environmental fluid was developed using Lagrangian method, in which the time mean velocity of the fluid was ca...A new mathematical model, fluctuation spectrum random trajectory model (FSRTM) for the particle motion in environmental fluid was developed using Lagrangian method, in which the time mean velocity of the fluid was calculated by a time mean velocity formula for two dimensional homogeneous shear turbulent flows in open channel, the velocity fluctuation of the fluid was determined by Fourier expansion and fluctuation spectrum, and the particle motion equation was solved using Ronge Kutta method. For comparison, the spherical cation exchange resins with a density of 1 44 g/cm\+3 and diameters ranging from 0 50—0 60 mm, 0 60—0 70 mm and 0 80—0 90 mm were selected as the experimental solid particles, and their moving velocities and trajectories in shear turbulent flows with the flow Reynolds number of 4710, 10240, 11900 and 20760 were investigated. The comparing analyses of the modeled results with the measured results have shown that the model developed in this paper can describe the motions of the particles in shear turbulent flow.展开更多
This study proposes a novel cyclone separator with a conical inner core to enhance particle classification efficiency in oil and gas wellhead-recovered liquids.Particle motion and force dynamics are analyzed to optimi...This study proposes a novel cyclone separator with a conical inner core to enhance particle classification efficiency in oil and gas wellhead-recovered liquids.Particle motion and force dynamics are analyzed to optimize key structural parameters,including inlet diameter(D_i),overflow pipe diameter(D_(e)),insertion depth(L_(e)),and bottom flow pipe diameter(D_(z)).Numerical simulations employ the Reynolds stress turbulence model,SIMPLEC algorithm,and discrete phase model to evaluate separation performance in a gas-liquid two-phase system.Results indicate that a smaller D_i improves fine particle separation but increases turbulence;an optimal range of D_i/D_(c)=0.35-0.4 is recommended.Larger D_(e) enhances the diversion ratio,aiding fine particle discharge(D_(e)/D_(c)=0.25-0.35).Increased Le facilitates fine particle overflow but induces vortices,whereas a smaller L_(e) stabilizes the bottom flow for larger particle separation(L_(e)/D_(c)=0.5-0.75).A reduced D_(z) enhances centrifugal force and separation efficiency but may cause turbulence;an optimal D_(z)/D_(c) of 0.6-0.65 is suggested for stability.These findings provide valuable design guidelines for improving cyclone separator performance in multiphase flow applications.展开更多
To enhance the performance and service life of the operating instrument in the food production process,the purpose of this paper is to study particle motion in a forced vortex flow condition as a way of performance im...To enhance the performance and service life of the operating instrument in the food production process,the purpose of this paper is to study particle motion in a forced vortex flow condition as a way of performance improvement.To solve the nonlinear equations of motion for the fine particle,a meshless Galerkin technique is applied.After declaring the proper accuracy of the results by comparison with existing research papers,the influences of some critical parameters on the particle movement have been examined.The radial part of the sphere velocity increases when the sphere size increases.However,this radial velocity is reduced by enhancing the sphere's initial velocity.For all situations,the sphere's velocity reduction is observed over time.展开更多
Simulation of straw grinding process based on discrete element method(DEM)was proposed.According to the force analysis and kinematics analysis,the differential equation of straw particle motion on hammers was deduced,...Simulation of straw grinding process based on discrete element method(DEM)was proposed.According to the force analysis and kinematics analysis,the differential equation of straw particle motion on hammers was deduced,and the formation mechanism of the material circulation layer was obtained.Geometric model of grinder,particle model and contact model were established by EDEM software.The influence of hammer number,hammer thickness and gap of the hammer-sieve on particle grinding number and power consumption were obtained by single factor simulation test.The grinding process is divided into three stages.The hammer smashing plays a dominant role in 0-0.25 s.While the hammer smashing particle number increases slowly and then decreases to the lowest level in 0.25-0.60 s,the tooth plate smashing particle number increases rapidly and dominates,and then forming a material circulation layer.The hammer and tooth plate smashing particle number is basically stable in 0.60-2.00 s,and the tooth plate smashing occupies the dominant position.With the increase of the number and thickness of hammers,the power consumption of crusher tends to increase,and with the increase of the gap between hammers and sieves,the power consumption of crusher decreases first and then increases.The results can provide guidance for the development of high-efficiency and energy-saving grinding equipment for cucumber straw.展开更多
The purpose of this study is to establish the high-accurate prediction method of particle separation in a cyclone separator. Numerical simulation of the swirling flows in a cyclone separator is performed by using a la...The purpose of this study is to establish the high-accurate prediction method of particle separation in a cyclone separator. Numerical simulation of the swirling flows in a cyclone separator is performed by using a large eddy simulation （LES） based on a Smagorinsky model. The validity of the simulation and the complicated flow characteristics are discussed by comparison with experimental results. Moreover, particle motions are treated by a Lagrangian method and are calculated with a one-way method. A performance for particle separation is predicted from the results of the particle tracing. As results of our investigation, the influences of the inserted height of the outlet pipe on the performance for particle separation of cyclone separator are shown.展开更多
Bedload studies at the particle scale may help grasp the essence of the problem.Existing studies suffer from short filming durations,limited data volume,and a narrow range of sediment transport intensity variations.Th...Bedload studies at the particle scale may help grasp the essence of the problem.Existing studies suffer from short filming durations,limited data volume,and a narrow range of sediment transport intensity variations.This paper employs the high-speed photography technology and conducts experimental studies on bedload particle motion under 8 different sediment transport intensities.Using the latest image processing technology,over 6 million sediment particle coordinate points and nearly 400,000 particle motion trajectory curves were automatically obtained and used to compare the motion characteristics of bedload particles under different sediment transport intensities.The results show that under low sediment transport intensity,both the number of moving particles and particle motion velocity contribute to the bedload sediment transport rate,while under high-intensity conditions,the transport rate mainly depends on the number of moving particles.The probability density distribution of sediment transport rate is concentrated and varies within a small range under low-intensity conditions,exhibiting a tailing phenomenon.In contrast,under high-intensity conditions,the range of sediment transport rate values increases,and the probability density curve tends to be symmetric,more closely approximating a normal distribution.Additionally,the paper compares the longitudinal and transverse motion velocities of particles and the coefficient of variation of the bedload sediment transport rate.展开更多
In a two-phase flow, the vortex merging influences both the flow evolution and the particle motion. With the blobs-splitting-and-merging scheme, the vortex merging is calculated by a corrected core spreading vortex me...In a two-phase flow, the vortex merging influences both the flow evolution and the particle motion. With the blobs-splitting-and-merging scheme, the vortex merging is calculated by a corrected core spreading vortex method （CCSVM）. The particle motion in the vortex merging process is calculated according to the particle kinetic model. The results indicate that the particle traces are spiral lines with the same rotation direction as the spinning vortex. The center of the particle group is in agreement with that of the merged vortex. The merging time is determined by the circulation and the initial ratio of the vortex radius and the vortex center distance. Under a certain initial condition, a stretched particle trail is generated, which is determined by the viscosity, the relative position between the particles and the vortex, and the asymmetrical circulation of the two merging vortices.展开更多
The flocculation behavior of carbon black (CB)-filled isoprene rubber (IR) nanocomposites was systematically investigated under both dynamic and static conditions to unravel the distinct mechanisms governing filler ne...The flocculation behavior of carbon black (CB)-filled isoprene rubber (IR) nanocomposites was systematically investigated under both dynamic and static conditions to unravel the distinct mechanisms governing filler network evolution.Under dynamic conditions,small oscillatory shear strains (0.1%) significantly enhanced filler particle motion,leading to pronounced agglomeration and a flocculation degree of about 4.3MPa at 145℃.In contrast,static flocculation exhibited a fundamentally different mechanism dominated by polymer chain dynamics,which is driven mainly by thermal activation.Radial distribution function (RDF) analysis of transmission electron microscopy (TEM) images revealed a slight decrease (2 nm) in the interparticle distance peak after static annealing at 100℃ for 7 h,indicating localized motion of CB particles.However,the overall filler network remained stable,with no significant agglomeration observed.The increase in bound rubber content from about 23% to 28% with rising temperature further confirmed the dominant role of polymer chain adsorption and interfacial reinforcement in static flocculation.These findings highlight the critical influence of external strain on filler network formation and provide new insights into the polymer-dominated mechanism of static flocculation.The results offer practical guidance for optimizing the storage and processing of rubber nanocomposites,particularly in applications where static flocculation during prolonged storage is a concern.展开更多
In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The ...In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The results show that the main resistance forces as the tracing particles settled in an air-solid MSFB were motion resistance force and yield force.The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles.The acceleration decreased from 3022.62 cm/s 2 to zero in 0.1 s,and in the end,the particles stopped in the air-solid MSFB.The yield force on particles increased with increasing the magnetic field intensity,resulting in decrease of the quasi-zero settling displacement.However,the yield force on particles decreased with increasing the fluidized air velocity,leading to increase of the quasi-zero settling displacement.When the structure and operating parameters of the air-solid MSFB were set up,the yield stress on particles stopped in an air-solid MSFB was a function of diameter and density of particles.The settling displacements of equal diameter particles increased with increasing their densities,and the settling displacements of equal density particles increased with increasing their diameters.展开更多
In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.Bu...In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.But such an approach has not been proved rigorously,and its accuracy must be carefully considered.In this paper,we discuss the problem of a sphere moving in a non-uniform flow field,on the basis of the fundamental theory of hydrodynamics.We introduce two assumptions:i)the diameter of the sphere is much smaller than the linear dimension of the flow field,and ii)the velocity of the sphere relative to the surrounding water is very small.Using these two assumptions,we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform,and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.展开更多
Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swar...Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swarm motion.In the model,we added a polar alignment strength,along with Gaussian curvature,affecting particles swarm motion.We find that when the force exceeds a certain limit,the order parameter will decrease with the increase of the force.Combined with our definition of order parameter and observation of the model,the reason is that particles begin to move side by side under the influence of polar forces.In addition,the effects of velocity,rotational diffusion coefficient,and packing fraction on particle swarm motion are discussed.It is found that the rotational diffusion coefficient and the packing fraction have a great influence on the clustering motion of particles,while the velocity has little influence on the clustering motion of particles.展开更多
Based on the coupfing between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found th...Based on the coupfing between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found that the motion of a spinning particle deviates from the geodesic trajectory, and this deviation originates from the coupling between the spin of the particle and gravitoelectromagnetic field, which is also the origin of Lense-Thirring effects. In post-Newtonian approximations, this equation gives the same results as those of Mathisson-Papapetrou equation. Effect of the deviation of geodesic trajectory is detectable.展开更多
The equation governing the motion of a quantum particle is considered in nonrelativistic non-commutative phase space. For this aim, we first study new Poisson brackets in non-commutative phase space and obtain the mod...The equation governing the motion of a quantum particle is considered in nonrelativistic non-commutative phase space. For this aim, we first study new Poisson brackets in non-commutative phase space and obtain the modified equations of motion. Next, using novel transformations, we solve the equation of motion and report the exact analytical solutions.展开更多
Different types of models for describing the motion of a kicked ion were suggested and studied. It is shown that certain kinds of jumping behavior of the exerting electromagnetic field can lead to a type of noninverti...Different types of models for describing the motion of a kicked ion were suggested and studied. It is shown that certain kinds of jumping behavior of the exerting electromagnetic field can lead to a type of noninvertible property, which changes this conservative system into a 'quasi-dissipative' one. The quasi-dissipative behaviors allow the particle to move along a confined chaotic 'quasi-attractor' in many regions of the parameter space. If the exerting electromagnetic field is discontinuous but the system is still invertible, it will take an unbounded chaotic diffusion with similar parameter values. We hope that this discovery could provide a helpful idea for confining the plasma.展开更多
For any study ofa suspension entering a pore, the knowledge of the force and moment exerted on a solute particle in an arbitrary position outside the pore is essential, 'This paper for the first lime presents appr...For any study ofa suspension entering a pore, the knowledge of the force and moment exerted on a solute particle in an arbitrary position outside the pore is essential, 'This paper for the first lime presents approximate analytical expressions (in closed form) of all the twelve force and moment coefficienis for a sphere outsied a circular orifice, on the basis of a number of discrete data computed by Yan et al(1987).These coefficients are then applied to calculate the trajectory and angular velocity of a spherical particle approaching the pore at zero Reynolds number. The trajectory is in excellent agreement with the available experimental results. An analysis of the relative importance of the coefficients shows that the rotation effect cannot be neglected near the pore opening or near the wall, and that the lateral force effect must be taken into account in the neighborhood of the edge of the pore opening. It is due to neglecting these factors that previous theoretical results deviate from the experimental ones near the pore opening. The effects of the ratio of the particle to pore radii as well as the influences of the graritytbuoyance on the particle trajectory, velocity distribution and rotation are discnssed in detail. It is pointed out that in the experiments of neutrally-buoyant suspensions, the restriction on the density of the particle is most demanding for a large particle size.The expressions of forces and moments presenled herein are complete, relatively accurate and convenient, thus providing a good prerequisite for further studies of any problems involving the entrance of particles to a pare.展开更多
The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The d...The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The difference of velocities gives a functional dependent solely on the velocity frame and original velocity of the particle. An analysis applied to the functional gives simple formulae for the extremal values of the mentioned velocity parameters. In the next step, solutions of the equation presented with the functional provide us with the velocities necessary for the vanishing property of the kinetic energy. A characteristic point is that a condition of the velocity of the motion frame smaller than the velocity of light is obtained directly in the applied formalism. This property holds with no reference done to the well-known postulate of the dominant value of the light velocity entering the relativity theory.展开更多
基金supported by NSF grant EAR-063566(F.N.)National Natural Science Foundation of China grant 40774042(J.L.)
文摘The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850＋ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth＇s deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the northcomponent azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.
基金supported by National Natural Science Foundation of China (Grant No. 50476068)Jiangsu Provincial Postgraduate Cultivation Innovation Project of China (Grant No. CX07B_093z)
文摘The vortex pump is suitable for salt solution transportation. But the salt-out flow mechanism in the pump has not been understood fully. Salt-out layer formation and growth rate are closely related to crystal particle motion and concentration distribution. Study on the particle hydrodynamic characteristics in the pump volute becomes a key problem, because the crystal particles are mainly distributing in this zone after they enter the pump. Phase Doppler particle analyzer（PDPA） is used to measure the two-phase flow field in a model pump volute to get more understanding about the salt-out phenomenon. The crystal particle velocities are obtained in all three peripheral, radial and axial directions. Particle size and particle number density（PND） measurements are also performed in the experiment. Results are presented and discussed along the radial direction under different pump operating conditions, as well as various axial measurement positions. It is found that particle velocity gradient of peripheral component varies with the pump discharge. There is a turning point of relation between peripheral velocity component and discharge. Radial flow velocity curves look like a saddle shape and velocity magnitudes are changing greatly with the discharge. The non-equilibrium velocity feature between liquid and solid phase on this direction is also remarkable. Particles flow into the impeller at radial position R〈I, and the axial velocity component increases in this region. The particle size curve shows an open-up parabola distribution. The largest particles are distributing near the casing peripheral wall. As flow rate increases, accordingly PND increases. It also grows up in the axial-outward direction towards the suction cover. Crystal particle aggregation phenomenon can be revealed from the analysis of particle size and PND distribution, and the aggregation region is determined as well. Research results are helpful for optimal design of this kind of pump preventing salt-out.
基金financially supported by the National Natural Science Foundation of China(Grant No.51275031)
文摘The particle motion behavior affects the distribution of particles in the metal matrix and finally determines the mechanical properties of the particle reinforced metal-matrix composites. To obtain a uniform distribution of TiC particles and excellent strengthening effect in 20%TiC/ZG270-500 composites fabricated by lost foam-squeeze casting （LFSC）, the particle motion behavior in the gas gap and the conditions of the particles getting into the molten steel were investigated. The results show that the airflow velocity （vl） and TiC particle motion velocity （up） change little with the pouring temperature （Tp）, increase with an increase in metal filling velocity （Vp）, ratios of cross sections of in-gate/orifice （AAAo） and orifice/mould cavity （AolAI）, but the increase trend of up is more intense. The airflow pressure （P1） changes little with Tp and Ao/A1, but increases with the increasing of vp and AJAo. Besides, there is a critical velocity （v ＋｜3YLG cosθ/ppdp｜1/2）for the particles getting into the molten steel. The higher the particle motion velocity, the easier the particles get into the molten steel and the more uniform the distribution of the particles in the steel matrix. When Tp = 1,873 K, vp = 30 mm.s-1, AJAo =10 and Ao/AI = 0.02 in this study, the biggest TiC particle motion velocity （20.59 m.s-~） can be gained, and the steel matrix with the most uniformly distributed TiC particles and fine grains are obtained.
文摘Fluid particles in translating surface gravity waves have an orbital motion which decreases in size with increasing mean depth. These wave characteristics came from observations and were not forecast theoretically. The classical potential flow model is incapable of explaining the particle movement due to the irrotational assumption and to a flaw in carrying out the method. When a wave passes by an observer from left to right, the particles move clockwise under a crest and a trough. This correct conclusion is consistent with what the incorrect standard theory implies but should not be considered to have been derived from it.
文摘A new mathematical model, fluctuation spectrum random trajectory model (FSRTM) for the particle motion in environmental fluid was developed using Lagrangian method, in which the time mean velocity of the fluid was calculated by a time mean velocity formula for two dimensional homogeneous shear turbulent flows in open channel, the velocity fluctuation of the fluid was determined by Fourier expansion and fluctuation spectrum, and the particle motion equation was solved using Ronge Kutta method. For comparison, the spherical cation exchange resins with a density of 1 44 g/cm\+3 and diameters ranging from 0 50—0 60 mm, 0 60—0 70 mm and 0 80—0 90 mm were selected as the experimental solid particles, and their moving velocities and trajectories in shear turbulent flows with the flow Reynolds number of 4710, 10240, 11900 and 20760 were investigated. The comparing analyses of the modeled results with the measured results have shown that the model developed in this paper can describe the motions of the particles in shear turbulent flow.
基金supported by the National Natural Science Foundation of China(52074341)。
文摘This study proposes a novel cyclone separator with a conical inner core to enhance particle classification efficiency in oil and gas wellhead-recovered liquids.Particle motion and force dynamics are analyzed to optimize key structural parameters,including inlet diameter(D_i),overflow pipe diameter(D_(e)),insertion depth(L_(e)),and bottom flow pipe diameter(D_(z)).Numerical simulations employ the Reynolds stress turbulence model,SIMPLEC algorithm,and discrete phase model to evaluate separation performance in a gas-liquid two-phase system.Results indicate that a smaller D_i improves fine particle separation but increases turbulence;an optimal range of D_i/D_(c)=0.35-0.4 is recommended.Larger D_(e) enhances the diversion ratio,aiding fine particle discharge(D_(e)/D_(c)=0.25-0.35).Increased Le facilitates fine particle overflow but induces vortices,whereas a smaller L_(e) stabilizes the bottom flow for larger particle separation(L_(e)/D_(c)=0.5-0.75).A reduced D_(z) enhances centrifugal force and separation efficiency but may cause turbulence;an optimal D_(z)/D_(c) of 0.6-0.65 is suggested for stability.These findings provide valuable design guidelines for improving cyclone separator performance in multiphase flow applications.
基金the Deanship of Research and Graduate Studies at King Khalid University for funding this work through Large Research Project under grant number RGP2/171/45。
文摘To enhance the performance and service life of the operating instrument in the food production process,the purpose of this paper is to study particle motion in a forced vortex flow condition as a way of performance improvement.To solve the nonlinear equations of motion for the fine particle,a meshless Galerkin technique is applied.After declaring the proper accuracy of the results by comparison with existing research papers,the influences of some critical parameters on the particle movement have been examined.The radial part of the sphere velocity increases when the sphere size increases.However,this radial velocity is reduced by enhancing the sphere's initial velocity.For all situations,the sphere's velocity reduction is observed over time.
基金This work was supported by the National Key Technologies R&D Program of China(No.2014BAD08B04)and the National Natural Science Fund of China(No.51175230,No.51475212)and the Funding for Key R&D Programs in Jiangsu Province(BE2018321).
文摘Simulation of straw grinding process based on discrete element method(DEM)was proposed.According to the force analysis and kinematics analysis,the differential equation of straw particle motion on hammers was deduced,and the formation mechanism of the material circulation layer was obtained.Geometric model of grinder,particle model and contact model were established by EDEM software.The influence of hammer number,hammer thickness and gap of the hammer-sieve on particle grinding number and power consumption were obtained by single factor simulation test.The grinding process is divided into three stages.The hammer smashing plays a dominant role in 0-0.25 s.While the hammer smashing particle number increases slowly and then decreases to the lowest level in 0.25-0.60 s,the tooth plate smashing particle number increases rapidly and dominates,and then forming a material circulation layer.The hammer and tooth plate smashing particle number is basically stable in 0.60-2.00 s,and the tooth plate smashing occupies the dominant position.With the increase of the number and thickness of hammers,the power consumption of crusher tends to increase,and with the increase of the gap between hammers and sieves,the power consumption of crusher decreases first and then increases.The results can provide guidance for the development of high-efficiency and energy-saving grinding equipment for cucumber straw.
文摘The purpose of this study is to establish the high-accurate prediction method of particle separation in a cyclone separator. Numerical simulation of the swirling flows in a cyclone separator is performed by using a large eddy simulation （LES） based on a Smagorinsky model. The validity of the simulation and the complicated flow characteristics are discussed by comparison with experimental results. Moreover, particle motions are treated by a Lagrangian method and are calculated with a one-way method. A performance for particle separation is predicted from the results of the particle tracing. As results of our investigation, the influences of the inserted height of the outlet pipe on the performance for particle separation of cyclone separator are shown.
基金National Natural Science Foundation of China,Grant/Award Numbers:12072373,51679260China Institute of Water Resources and Hydropower Research,Grant/Award Number:SE0145B022021。
文摘Bedload studies at the particle scale may help grasp the essence of the problem.Existing studies suffer from short filming durations,limited data volume,and a narrow range of sediment transport intensity variations.This paper employs the high-speed photography technology and conducts experimental studies on bedload particle motion under 8 different sediment transport intensities.Using the latest image processing technology,over 6 million sediment particle coordinate points and nearly 400,000 particle motion trajectory curves were automatically obtained and used to compare the motion characteristics of bedload particles under different sediment transport intensities.The results show that under low sediment transport intensity,both the number of moving particles and particle motion velocity contribute to the bedload sediment transport rate,while under high-intensity conditions,the transport rate mainly depends on the number of moving particles.The probability density distribution of sediment transport rate is concentrated and varies within a small range under low-intensity conditions,exhibiting a tailing phenomenon.In contrast,under high-intensity conditions,the range of sediment transport rate values increases,and the probability density curve tends to be symmetric,more closely approximating a normal distribution.Additionally,the paper compares the longitudinal and transverse motion velocities of particles and the coefficient of variation of the bedload sediment transport rate.
基金Project supported by the National Natural Science Foundation of China (No. 10572020)
文摘In a two-phase flow, the vortex merging influences both the flow evolution and the particle motion. With the blobs-splitting-and-merging scheme, the vortex merging is calculated by a corrected core spreading vortex method （CCSVM）. The particle motion in the vortex merging process is calculated according to the particle kinetic model. The results indicate that the particle traces are spiral lines with the same rotation direction as the spinning vortex. The center of the particle group is in agreement with that of the merged vortex. The merging time is determined by the circulation and the initial ratio of the vortex radius and the vortex center distance. Under a certain initial condition, a stretched particle trail is generated, which is determined by the viscosity, the relative position between the particles and the vortex, and the asymmetrical circulation of the two merging vortices.
基金supported by the National Natural Science Foundation of China(No.52293471)National Key R&D Program of China(No.2022YFB3707303).
文摘The flocculation behavior of carbon black (CB)-filled isoprene rubber (IR) nanocomposites was systematically investigated under both dynamic and static conditions to unravel the distinct mechanisms governing filler network evolution.Under dynamic conditions,small oscillatory shear strains (0.1%) significantly enhanced filler particle motion,leading to pronounced agglomeration and a flocculation degree of about 4.3MPa at 145℃.In contrast,static flocculation exhibited a fundamentally different mechanism dominated by polymer chain dynamics,which is driven mainly by thermal activation.Radial distribution function (RDF) analysis of transmission electron microscopy (TEM) images revealed a slight decrease (2 nm) in the interparticle distance peak after static annealing at 100℃ for 7 h,indicating localized motion of CB particles.However,the overall filler network remained stable,with no significant agglomeration observed.The increase in bound rubber content from about 23% to 28% with rising temperature further confirmed the dominant role of polymer chain adsorption and interfacial reinforcement in static flocculation.These findings highlight the critical influence of external strain on filler network formation and provide new insights into the polymer-dominated mechanism of static flocculation.The results offer practical guidance for optimizing the storage and processing of rubber nanocomposites,particularly in applications where static flocculation during prolonged storage is a concern.
基金supported by the National Natural Science Foundation of China (Nos. 51134022 and 51174203)the Key Project of Chinese National Programs for Fundamental Research and Development (No. 2012CB214904)+2 种基金the National Natural Science Foundation of China for Innovative Research Group (No. 50921002)the Natural Science Foundation of Jiangsu Province (No. BK2010002)the Fundamental Research Funds for the Central Universities (Nos. 2010QNB11 and 2010ZDP01A06)
文摘In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The results show that the main resistance forces as the tracing particles settled in an air-solid MSFB were motion resistance force and yield force.The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles.The acceleration decreased from 3022.62 cm/s 2 to zero in 0.1 s,and in the end,the particles stopped in the air-solid MSFB.The yield force on particles increased with increasing the magnetic field intensity,resulting in decrease of the quasi-zero settling displacement.However,the yield force on particles decreased with increasing the fluidized air velocity,leading to increase of the quasi-zero settling displacement.When the structure and operating parameters of the air-solid MSFB were set up,the yield stress on particles stopped in an air-solid MSFB was a function of diameter and density of particles.The settling displacements of equal diameter particles increased with increasing their densities,and the settling displacements of equal density particles increased with increasing their diameters.
文摘In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.But such an approach has not been proved rigorously,and its accuracy must be carefully considered.In this paper,we discuss the problem of a sphere moving in a non-uniform flow field,on the basis of the fundamental theory of hydrodynamics.We introduce two assumptions:i)the diameter of the sphere is much smaller than the linear dimension of the flow field,and ii)the velocity of the sphere relative to the surrounding water is very small.Using these two assumptions,we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform,and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12075090 and 12005066)the Science and Technology Program of Guangzhou(Grant No.2019050001)+1 种基金the Natural Science Foundation of Guangdong Province,China(Grant No.2017A030313029)the Major Basic Research Project of Guangdong Province,China(Grant No.2017KZDXM024)。
文摘Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swarm motion.In the model,we added a polar alignment strength,along with Gaussian curvature,affecting particles swarm motion.We find that when the force exceeds a certain limit,the order parameter will decrease with the increase of the force.Combined with our definition of order parameter and observation of the model,the reason is that particles begin to move side by side under the influence of polar forces.In addition,the effects of velocity,rotational diffusion coefficient,and packing fraction on particle swarm motion are discussed.It is found that the rotational diffusion coefficient and the packing fraction have a great influence on the clustering motion of particles,while the velocity has little influence on the clustering motion of particles.
文摘Based on the coupfing between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found that the motion of a spinning particle deviates from the geodesic trajectory, and this deviation originates from the coupling between the spin of the particle and gravitoelectromagnetic field, which is also the origin of Lense-Thirring effects. In post-Newtonian approximations, this equation gives the same results as those of Mathisson-Papapetrou equation. Effect of the deviation of geodesic trajectory is detectable.
基金Supported by the China Scholarship Councilthe Hanjiang Scholar Project of Shaanxi University of Technology
文摘The equation governing the motion of a quantum particle is considered in nonrelativistic non-commutative phase space. For this aim, we first study new Poisson brackets in non-commutative phase space and obtain the modified equations of motion. Next, using novel transformations, we solve the equation of motion and report the exact analytical solutions.
基金the National Natural Foundation of China under Grant No. 19975039.
文摘Different types of models for describing the motion of a kicked ion were suggested and studied. It is shown that certain kinds of jumping behavior of the exerting electromagnetic field can lead to a type of noninvertible property, which changes this conservative system into a 'quasi-dissipative' one. The quasi-dissipative behaviors allow the particle to move along a confined chaotic 'quasi-attractor' in many regions of the parameter space. If the exerting electromagnetic field is discontinuous but the system is still invertible, it will take an unbounded chaotic diffusion with similar parameter values. We hope that this discovery could provide a helpful idea for confining the plasma.
基金Project supported by the National Natural Science Foundation of China
文摘For any study ofa suspension entering a pore, the knowledge of the force and moment exerted on a solute particle in an arbitrary position outside the pore is essential, 'This paper for the first lime presents approximate analytical expressions (in closed form) of all the twelve force and moment coefficienis for a sphere outsied a circular orifice, on the basis of a number of discrete data computed by Yan et al(1987).These coefficients are then applied to calculate the trajectory and angular velocity of a spherical particle approaching the pore at zero Reynolds number. The trajectory is in excellent agreement with the available experimental results. An analysis of the relative importance of the coefficients shows that the rotation effect cannot be neglected near the pore opening or near the wall, and that the lateral force effect must be taken into account in the neighborhood of the edge of the pore opening. It is due to neglecting these factors that previous theoretical results deviate from the experimental ones near the pore opening. The effects of the ratio of the particle to pore radii as well as the influences of the graritytbuoyance on the particle trajectory, velocity distribution and rotation are discnssed in detail. It is pointed out that in the experiments of neutrally-buoyant suspensions, the restriction on the density of the particle is most demanding for a large particle size.The expressions of forces and moments presenled herein are complete, relatively accurate and convenient, thus providing a good prerequisite for further studies of any problems involving the entrance of particles to a pare.
文摘The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The difference of velocities gives a functional dependent solely on the velocity frame and original velocity of the particle. An analysis applied to the functional gives simple formulae for the extremal values of the mentioned velocity parameters. In the next step, solutions of the equation presented with the functional provide us with the velocities necessary for the vanishing property of the kinetic energy. A characteristic point is that a condition of the velocity of the motion frame smaller than the velocity of light is obtained directly in the applied formalism. This property holds with no reference done to the well-known postulate of the dominant value of the light velocity entering the relativity theory.
