Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of n...Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of non-spherical particles considering particle drag correction,lift,and rotation was established.Based on the Eulerian-Lagrangian simulation,the dispersion characteristics of spherical and nonspherical particles with different Stokes numbers in a high-speed turbulent jet were analyzed and compared considering the effect of particle rotation.The results show that,the differences in particle dispersion and radial velocity fluctuation between non-spherical particles and spherical particles in the jet are significant,especially when Stokes number is large.Moreover,the effects of different type of forces on the dispersion of non-spherical particles and spherical particles were compared in detail,which revealed that the change of the Magnus force caused by the increase in the angular velocity of non-spherical particles plays a dominant role in the differences of particle dispersion.展开更多
Particle rotation plays an important role in gas-solid flows. This paper presents an experimental investigation on the spatial distribution of average rotation speed for glass beads in the upper dilute zone of a cold ...Particle rotation plays an important role in gas-solid flows. This paper presents an experimental investigation on the spatial distribution of average rotation speed for glass beads in the upper dilute zone of a cold circulating fluidized bed(CFB) riser. It is shown that in the horizontal direction,the average rotation speed in the near-wall area is larger than that in the center area,while in the vertical direction,it decreases as the height increases. The reason resulting in this distribution is analyzed by considering several factors including particle size,particle shape,particle number density,particle collision behavior,and the surrounding flow field,etc. The effects of CFB operation conditions on the spatial distribution of average rotation speed are also studied. The results show that the increasing superficial gas velocity increases the average rotation speed of particles in the near wall area but takes nearly no effect on that in the center area. The external solids mass flux,however,takes the opposite effect. It is found that the average rotation speeds of particles in both areas are increased as the total amount of bed material increases.展开更多
To investigate the influence of snow particle rotational motion on the accumulation of snow in the bogie region of high-speed trains,an Euler‒Lagrange numerical approach is adopted.The study examines the effects of sn...To investigate the influence of snow particle rotational motion on the accumulation of snow in the bogie region of high-speed trains,an Euler‒Lagrange numerical approach is adopted.The study examines the effects of snow particle diameter and train speed on the ensuing dynamics.It is shown that considering snow particle rotational motion causes significant deviation in the particle trajectories with respect to non-rotating particles.Such a deviation increases with larger snow particle diameters and higher train speeds.The snow accumulation on the overall surface of the bogie increases,and the amount of snow on the vibration reduction device varies greatly.In certain conditions,the amount of accumulated snow can increase by several orders of magnitudes.展开更多
We derive the Schr6dinger equation of a particle constrained to move on a rotating curved surface S. Using the thin-layer quantization scheme to confine the particle on S, and with a proper choice of gauge transformat...We derive the Schr6dinger equation of a particle constrained to move on a rotating curved surface S. Using the thin-layer quantization scheme to confine the particle on S, and with a proper choice of gauge transformation for the wave function, we obtain the well-known geometric potentiM Vg and an additive Coriolis-induced geometric potential in the co-rotationM curvilinear coordinates. This novel effective potential, which is included in the surface Schr6dinger equation and is coupled with the mean curvature of S, contains an imaginary part in the general case which gives rise to a non-Hermitian surface Hamiltonian. We find that the non-Hermitian term vanishes when S is a minimal surface or a revolution surface which is axially symmetric around the rolling axis.展开更多
Based on a first-principles approach,we establish an alternating-current（AC） relaxation theory for a rotating metallic particle with complex dielectric constant εα=εα-iσα/ω0.Here εα is the real part,σα th...Based on a first-principles approach,we establish an alternating-current（AC） relaxation theory for a rotating metallic particle with complex dielectric constant εα=εα-iσα/ω0.Here εα is the real part,σα the conductivity,ω0 the angular frequency of an AC electric field,and i=-11/2.Our theory yields an accurate interparticle force,which is in good agreement with the existing experiment.The agreement helps to show that the relaxations of two kinds of charges,namely,surface polarized charges（described by εα） and free charges（corresponding to σα）,contribute to the unusually large reduction in the attracting interparticle force.This theory can be adopted to determine the relaxation time of dynamic particles in various fields.展开更多
We investigate the massive vector particles' Hawking radiation from the neutral rotating Anti-de Sitter(AdS) black holes in conformal gravity by using the tunneling method.It is well known that the dynamics of mas...We investigate the massive vector particles' Hawking radiation from the neutral rotating Anti-de Sitter(AdS) black holes in conformal gravity by using the tunneling method.It is well known that the dynamics of massive vector particles are governed by the Proca field equation.Applying WKB approximation to the Proca equation,the tunneling probabilities and radiation spectrums of the emitted particles are derived.Hawking temperature of the neutral rotating AdS black holes in conformal gravity is recovered,which is consistent with the previous result in the literature.展开更多
Computational fluid dynamics-discrete element method(CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions...Computational fluid dynamics-discrete element method(CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions of millions of particles with complex interactions with liquid and the rotating impeller. The simulations were satisfactorily validated with experimental data in literature in terms of measured particle velocities in the tank.Influences of operating conditions and physical properties of particles(i.e., particle diameter and density) on the two-phase flow field in the stirred tank involving particle distribution, particle velocity and vortex were studied.The wide distribution of particle angular velocity ranging from 0 to 105r·min 1is revealed. The Magnus force is comparable to the drag force during the particle movement in the tank. The strong particle rotation will generate extra shear force on the particles so that the particle morphology may be affected, especially in the bio-/polymer-product related processes. It can be concluded that the CFD-DEM coupled approach provides a theoretical way to understand the physics of particle movement in micro- to macro-scales in the solid suspension of a stirred tank.展开更多
This study investigates the effect of non-convexity on the rotational characteristics and contact mechanisms of two-dimensional star-like shapes using multiellipse-based discrete element modeling(DEM).Biaxial shearing...This study investigates the effect of non-convexity on the rotational characteristics and contact mechanisms of two-dimensional star-like shapes using multiellipse-based discrete element modeling(DEM).Biaxial shearing tests are conducted on star-shaped geometries with varying arm numbers and aspect ratios of the intersecting ellipses.The results indicate a non-monotonic relationship between overall particle rotation and increasing non-convexity,highlighting a more pronounced role of non-convexity in promoting local interlocking at particle contacts.Moreover,high non-convexity facilitates the formation of multiple contact points between interacting particles,which generally show higher stability than single-point contacts,except in the case of highly non-convex shapes.The geometric complexity introduced by non-convexity induces significant heterogeneity in the contact network and inter-particle force distributions.Finally,a spatial analysis of contact patterns reveals the coexistence of interlocking and excluded volume effects,where the alignment of the arms and valleys results in two distinct peaks in contact frequency and governs the initiation location of particle interactions.Meanwhile,the intermediate surfaces become less involved in particle contacts as non-convexity increases.展开更多
The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of ex...The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of external information;hence,it is especially suitable for measuring the angular and translational velocities of internal characteristic particles.To study the influence of the end wall of the chute on the motions of the internal characteristic particles,the z-axis rotational and translational velocities of the internal characteristic particles in the chute were measured,and it was found that the rotational velocity about the z-axis differs according to the initial position.The z-axis angular velocity of a characteristic particle at the centre fluctuates near 0,and the average value approaches 0.The z-axis angular velocity of a characteristic particle at the left end wall is typically negative.This phenomenon is due to the influence of the end wall on the rotational motions of particles with initial positions that are near the end wall.In addition,the average translational velocity of the characteristic particles is also affected by the end wall.The distributions of the average z-axis angular velocity and the average translational velocity are quantitatively analysed,and the correlation between the tilt angle of the chute and the end wall effect is studied.展开更多
The enantiospecific detection of the chirality of substances at the nanoscale has attracted significant attention due to its importance in materials science,chemistry,and biology.This study presents,to our knowledge,a...The enantiospecific detection of the chirality of substances at the nanoscale has attracted significant attention due to its importance in materials science,chemistry,and biology.This study presents,to our knowledge,a novel method for chirality detection based on transverse optical torque(OT),which leverages the transverse rotation of achiral particles induced by the transfer of chirality from the chiral particle within interference fields formed by the incident light without spin angular momentum(SAM).We demonstrate,both numerically and analytically,that by modulating the chirality of the chiral particle within a dimer system,it is possible to achieve the transfer of local SAM to the gold particle,thereby generating a transverse OT perpendicular to the light propagation direction.Furthermore,by adjusting the orientation of linear polarization in the excitation field,the respective contributions of electric and magnetic responses to the chirality-transfer-induced transverse OT can be exclusively observed separately,providing deeper insights into the underlying physical mechanisms.More importantly,the transverse OT exhibits an approximately linear dependence on the chirality parameter of the chiral particle,enabling enantiospecific detection of nanosamples.By replacing gold nanoparticles with suitable highrefractive-index dielectric materials such as germanium,the induced transverse magnetic dipolar OT can be further enhanced by more than two orders of magnitude,significantly improving the sensitivity of chirality detection and making it possible to detect weak chiral signals with exceptional precision.This work broadens the application scope of OTs in chirality detection and highlights the potential of chirality transfer mechanisms for advanced optical manipulation and the identification and analysis of chiral substances.展开更多
基金supported by National Science and Technology Major Project of China(2019-I-0022-0021)Seed fund of Shanxi Research Institute for Clean Energy,Tsinghua Universitythe National Natural Science Foundation of China(51761125011)。
文摘Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of non-spherical particles considering particle drag correction,lift,and rotation was established.Based on the Eulerian-Lagrangian simulation,the dispersion characteristics of spherical and nonspherical particles with different Stokes numbers in a high-speed turbulent jet were analyzed and compared considering the effect of particle rotation.The results show that,the differences in particle dispersion and radial velocity fluctuation between non-spherical particles and spherical particles in the jet are significant,especially when Stokes number is large.Moreover,the effects of different type of forces on the dispersion of non-spherical particles and spherical particles were compared in detail,which revealed that the change of the Magnus force caused by the increase in the angular velocity of non-spherical particles plays a dominant role in the differences of particle dispersion.
基金the National Key Technologies Supporting Program of China during the 11th Five-Year Plan Period (No. 2006BAA03B01)the China Postdoctoral Science Foundation(No. 20070421165)
文摘Particle rotation plays an important role in gas-solid flows. This paper presents an experimental investigation on the spatial distribution of average rotation speed for glass beads in the upper dilute zone of a cold circulating fluidized bed(CFB) riser. It is shown that in the horizontal direction,the average rotation speed in the near-wall area is larger than that in the center area,while in the vertical direction,it decreases as the height increases. The reason resulting in this distribution is analyzed by considering several factors including particle size,particle shape,particle number density,particle collision behavior,and the surrounding flow field,etc. The effects of CFB operation conditions on the spatial distribution of average rotation speed are also studied. The results show that the increasing superficial gas velocity increases the average rotation speed of particles in the near wall area but takes nearly no effect on that in the center area. The external solids mass flux,however,takes the opposite effect. It is found that the average rotation speeds of particles in both areas are increased as the total amount of bed material increases.
基金funded by The National Natural Science Foundation of China(Grant No.12172308)the Provincial Natural Science Foundation of Hunan(Grant No.2023JJ40260).
文摘To investigate the influence of snow particle rotational motion on the accumulation of snow in the bogie region of high-speed trains,an Euler‒Lagrange numerical approach is adopted.The study examines the effects of snow particle diameter and train speed on the ensuing dynamics.It is shown that considering snow particle rotational motion causes significant deviation in the particle trajectories with respect to non-rotating particles.Such a deviation increases with larger snow particle diameters and higher train speeds.The snow accumulation on the overall surface of the bogie increases,and the amount of snow on the vibration reduction device varies greatly.In certain conditions,the amount of accumulated snow can increase by several orders of magnitudes.
基金Supported by the National Natural Science Foundation of China under Grants Nos 11047020,11404157,11274166,11275097,11475085 and 11535005the Natural Science Foundation of Shangdong Province under Grants Nos ZR2012AM022 and ZR2011AM019
文摘We derive the Schr6dinger equation of a particle constrained to move on a rotating curved surface S. Using the thin-layer quantization scheme to confine the particle on S, and with a proper choice of gauge transformation for the wave function, we obtain the well-known geometric potentiM Vg and an additive Coriolis-induced geometric potential in the co-rotationM curvilinear coordinates. This novel effective potential, which is included in the surface Schr6dinger equation and is coupled with the mean curvature of S, contains an imaginary part in the general case which gives rise to a non-Hermitian surface Hamiltonian. We find that the non-Hermitian term vanishes when S is a minimal surface or a revolution surface which is axially symmetric around the rolling axis.
基金Project supported by the National Natural Science Foundation of China(Grant No.11222544)the Fok Ying Tung Education Foundation(Grant No.131008)+1 种基金the Program for New Century Excellent Talents in University,China(Grant No.NCET-12-0121)the National Key Basic Research Program of China(Grant No.2011CB922004)
文摘Based on a first-principles approach,we establish an alternating-current（AC） relaxation theory for a rotating metallic particle with complex dielectric constant εα=εα-iσα/ω0.Here εα is the real part,σα the conductivity,ω0 the angular frequency of an AC electric field,and i=-11/2.Our theory yields an accurate interparticle force,which is in good agreement with the existing experiment.The agreement helps to show that the relaxations of two kinds of charges,namely,surface polarized charges（described by εα） and free charges（corresponding to σα）,contribute to the unusually large reduction in the attracting interparticle force.This theory can be adopted to determine the relaxation time of dynamic particles in various fields.
基金Supported by the National Natural Science Foundation of China under Grant No.11205048the Foundation for Young Key Teacher of Henan Normal University
文摘We investigate the massive vector particles' Hawking radiation from the neutral rotating Anti-de Sitter(AdS) black holes in conformal gravity by using the tunneling method.It is well known that the dynamics of massive vector particles are governed by the Proca field equation.Applying WKB approximation to the Proca equation,the tunneling probabilities and radiation spectrums of the emitted particles are derived.Hawking temperature of the neutral rotating AdS black holes in conformal gravity is recovered,which is consistent with the previous result in the literature.
基金Supported by the State Key Development Program for Basic Research of China （2013CB733600）, the National Natural Science Foundation of China （21036003, 20776074） and the Specialized Research Fund for the Doctoral Program of Higher Education of China （20090002110069）.
文摘Computational fluid dynamics-discrete element method(CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions of millions of particles with complex interactions with liquid and the rotating impeller. The simulations were satisfactorily validated with experimental data in literature in terms of measured particle velocities in the tank.Influences of operating conditions and physical properties of particles(i.e., particle diameter and density) on the two-phase flow field in the stirred tank involving particle distribution, particle velocity and vortex were studied.The wide distribution of particle angular velocity ranging from 0 to 105r·min 1is revealed. The Magnus force is comparable to the drag force during the particle movement in the tank. The strong particle rotation will generate extra shear force on the particles so that the particle morphology may be affected, especially in the bio-/polymer-product related processes. It can be concluded that the CFD-DEM coupled approach provides a theoretical way to understand the physics of particle movement in micro- to macro-scales in the solid suspension of a stirred tank.
文摘This study investigates the effect of non-convexity on the rotational characteristics and contact mechanisms of two-dimensional star-like shapes using multiellipse-based discrete element modeling(DEM).Biaxial shearing tests are conducted on star-shaped geometries with varying arm numbers and aspect ratios of the intersecting ellipses.The results indicate a non-monotonic relationship between overall particle rotation and increasing non-convexity,highlighting a more pronounced role of non-convexity in promoting local interlocking at particle contacts.Moreover,high non-convexity facilitates the formation of multiple contact points between interacting particles,which generally show higher stability than single-point contacts,except in the case of highly non-convex shapes.The geometric complexity introduced by non-convexity induces significant heterogeneity in the contact network and inter-particle force distributions.Finally,a spatial analysis of contact patterns reveals the coexistence of interlocking and excluded volume effects,where the alignment of the arms and valleys results in two distinct peaks in contact frequency and governs the initiation location of particle interactions.Meanwhile,the intermediate surfaces become less involved in particle contacts as non-convexity increases.
基金This work has been supported by the National Natural Science Foundation of China(91634202,11902190).
文摘The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of external information;hence,it is especially suitable for measuring the angular and translational velocities of internal characteristic particles.To study the influence of the end wall of the chute on the motions of the internal characteristic particles,the z-axis rotational and translational velocities of the internal characteristic particles in the chute were measured,and it was found that the rotational velocity about the z-axis differs according to the initial position.The z-axis angular velocity of a characteristic particle at the centre fluctuates near 0,and the average value approaches 0.The z-axis angular velocity of a characteristic particle at the left end wall is typically negative.This phenomenon is due to the influence of the end wall on the rotational motions of particles with initial positions that are near the end wall.In addition,the average translational velocity of the characteristic particles is also affected by the end wall.The distributions of the average z-axis angular velocity and the average translational velocity are quantitatively analysed,and the correlation between the tilt angle of the chute and the end wall effect is studied.
基金National Natural Science Foundation of China(12274074,12134013,12174076)Natural Science Foundation of Jiangsu Province(BK20242024)+1 种基金Natural Science Foundation of Guangxi(2023GXNSFFA026002)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX24_0381)。
文摘The enantiospecific detection of the chirality of substances at the nanoscale has attracted significant attention due to its importance in materials science,chemistry,and biology.This study presents,to our knowledge,a novel method for chirality detection based on transverse optical torque(OT),which leverages the transverse rotation of achiral particles induced by the transfer of chirality from the chiral particle within interference fields formed by the incident light without spin angular momentum(SAM).We demonstrate,both numerically and analytically,that by modulating the chirality of the chiral particle within a dimer system,it is possible to achieve the transfer of local SAM to the gold particle,thereby generating a transverse OT perpendicular to the light propagation direction.Furthermore,by adjusting the orientation of linear polarization in the excitation field,the respective contributions of electric and magnetic responses to the chirality-transfer-induced transverse OT can be exclusively observed separately,providing deeper insights into the underlying physical mechanisms.More importantly,the transverse OT exhibits an approximately linear dependence on the chirality parameter of the chiral particle,enabling enantiospecific detection of nanosamples.By replacing gold nanoparticles with suitable highrefractive-index dielectric materials such as germanium,the induced transverse magnetic dipolar OT can be further enhanced by more than two orders of magnitude,significantly improving the sensitivity of chirality detection and making it possible to detect weak chiral signals with exceptional precision.This work broadens the application scope of OTs in chirality detection and highlights the potential of chirality transfer mechanisms for advanced optical manipulation and the identification and analysis of chiral substances.
