The occurrence of a mesoscopic scale in granular materials leads to a sharp increase in the number of interaction processes at both intra-and inter-scale levels.The mesoscopic scale is the main source of the complex m...The occurrence of a mesoscopic scale in granular materials leads to a sharp increase in the number of interaction processes at both intra-and inter-scale levels.The mesoscopic scale is the main source of the complex macroscopic properties of granular materials.The quantification of mesoscopic disordered movements is often referred to as granular temperature.In this paper,we first introduce the physical meaning of the original granular temperature of a kinetic nature,Tk,and then briefly summarize the advances made over the past few decades.Our research group has focused on Tk measurement using speckle visibility spectroscopy.The principle of this technique and the instruments developed in our research group are briefly introduced.Our work shows great promise in the measurement of kinetic granular temperature.Finally,a summary of granular temperature and some recent developments in speckle visibility spectroscopy measurements are presented.展开更多
The discrete hard sphere particle model （DPM） is applied in this work to study numerically the distribu- tions of particle and bubble granular temperatures in a bubbling fluidized bed. The dimensions of the bed and ...The discrete hard sphere particle model （DPM） is applied in this work to study numerically the distribu- tions of particle and bubble granular temperatures in a bubbling fluidized bed. The dimensions of the bed and other parameters are set to correspond to those of Miuller et al（2008）. Various drag models and oper- ational parameters are investigated to find their influence on particle and bubble granular temperatures. Various inlet superficial gas velocities are used in this work to obtain their effect on flow characteristics. It is found that the superficial gas velocity has the most important effect on granular temperatures including bubble granular temperature, particle translational granular temperature and particle rotational granular temperature. The drag force model affects more seriously the large scale variables such as the bubble gran- ular temperature. Restitution coefficient influences all granular temperatures to some degree. Simulation results are compared with experimental results by Muller et al. （2008） showing reasonable agreement.展开更多
A lower granular temperature zone near the orifice in silos was found by speckle visibility spectroscopy technology.Surprisingly,the values of granular temperature in this area are inversely proportional to the mass d...A lower granular temperature zone near the orifice in silos was found by speckle visibility spectroscopy technology.Surprisingly,the values of granular temperature in this area are inversely proportional to the mass discharge rate(MDR).This finding that links the macroscopic MDR with mesoscopic dynamics temperature of the particle system,is obtained by looking at the effect that different outlet sizes of silos on MDR and granular temperature field.Apart from evidencing the relevance of a parameter that has been traditionally overlooked in silos,this relationship supposes a benchmark with which to explore the influence of small orifice sizes on MDR.Among these,we found that the frequency of intermittent clogging and their dependence on the size of the outlet.展开更多
Numerical simulations are employed to consider the problem of determining the granular temperatures of the species of a homogeneous heated granular mixture with a power-law size distribution. The partial granular temp...Numerical simulations are employed to consider the problem of determining the granular temperatures of the species of a homogeneous heated granular mixture with a power-law size distribution. The partial granular temperature ratios are studied as functions of the fractal dimension D, the restitution coefflcient e, the rescaled viscosity time, the average occupied area fraction φ, the total particle number N and the number fraction. Different species of particles in a power-law system typically do not have the same mean kinetic energy, namely the granular temperature. It is found that the extent of nonequipartition of kinetic energy is determined by the fractal dimension D, the restitution coemcient e and the rescaled viscosity time, while is insensitive to the total particle number N, the area fraction φ and the number fraction.展开更多
Granular materials exhibit abundant dissipations due to fluctuations in both granular motions and configurations （i.e., granular skeleton） evolutions. Twin granular temperatures Tk and T~ are introduced accounting f...Granular materials exhibit abundant dissipations due to fluctuations in both granular motions and configurations （i.e., granular skeleton） evolutions. Twin granular temperatures Tk and T~ are introduced accounting for two types of fluctuations, and the so-called twin granular temperatures theory is established as an extension of granular solid hydrodynamics. By using simulations, the nonaffine deformations in a 2D assembly are simulated by using discrete element methods. By analogizing with microdamages in deformed solids, double scalar damage variables, Dp and Dq, are proposed to describe the deformed granular solid under triaxial compressions. Granular flows are found intrinsically turbulent due to the presence of Tk and the Naiver Stokes equation is obtained for granular flows.展开更多
Granular materials display more abundant dissipation phenomena than ordinary materials. In this paper, a brief energy flow path with irreversible processes is illustrated, where the concept of granular temperature Tg,...Granular materials display more abundant dissipation phenomena than ordinary materials. In this paper, a brief energy flow path with irreversible processes is illustrated, where the concept of granular temperature Tg, initially proposed for dilute systems, is extended to dense systems in order to quantify disordered force chain configurations. Additionally, we develop the concept of conjugate granular entropy sg and its production equation. Our analyses find out that the granular entropy significantly undermined the elastic contact between particles, seriously affecting the transport coefficients in granular materials and creating new transport processes.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11572201,11572178,and 91634202)the Innovation Program of Shanghai Municipal Education Commission(Grant No.15ZZ072).
文摘The occurrence of a mesoscopic scale in granular materials leads to a sharp increase in the number of interaction processes at both intra-and inter-scale levels.The mesoscopic scale is the main source of the complex macroscopic properties of granular materials.The quantification of mesoscopic disordered movements is often referred to as granular temperature.In this paper,we first introduce the physical meaning of the original granular temperature of a kinetic nature,Tk,and then briefly summarize the advances made over the past few decades.Our research group has focused on Tk measurement using speckle visibility spectroscopy.The principle of this technique and the instruments developed in our research group are briefly introduced.Our work shows great promise in the measurement of kinetic granular temperature.Finally,a summary of granular temperature and some recent developments in speckle visibility spectroscopy measurements are presented.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (Grant No. 51121004)the National Natural Science Foundation of China–China National Petroleum Corporation Joint Fund of Petrochemical Engineering (U1162122) the Program for New Century Excellent Talents in University (NCET-08-0159)
文摘The discrete hard sphere particle model （DPM） is applied in this work to study numerically the distribu- tions of particle and bubble granular temperatures in a bubbling fluidized bed. The dimensions of the bed and other parameters are set to correspond to those of Miuller et al（2008）. Various drag models and oper- ational parameters are investigated to find their influence on particle and bubble granular temperatures. Various inlet superficial gas velocities are used in this work to obtain their effect on flow characteristics. It is found that the superficial gas velocity has the most important effect on granular temperatures including bubble granular temperature, particle translational granular temperature and particle rotational granular temperature. The drag force model affects more seriously the large scale variables such as the bubble gran- ular temperature. Restitution coefficient influences all granular temperatures to some degree. Simulation results are compared with experimental results by Muller et al. （2008） showing reasonable agreement.
基金This work was supported by the National Natural Science Foundation of China(grant Nos.11972212,11902190,12072200,12002213)the Natural Science Foundation of Shanghai(grant No.20ZR1438800)Science and Technology Commission of Shanghai Municipality(grant No,19142201500).
文摘A lower granular temperature zone near the orifice in silos was found by speckle visibility spectroscopy technology.Surprisingly,the values of granular temperature in this area are inversely proportional to the mass discharge rate(MDR).This finding that links the macroscopic MDR with mesoscopic dynamics temperature of the particle system,is obtained by looking at the effect that different outlet sizes of silos on MDR and granular temperature field.Apart from evidencing the relevance of a parameter that has been traditionally overlooked in silos,this relationship supposes a benchmark with which to explore the influence of small orifice sizes on MDR.Among these,we found that the frequency of intermittent clogging and their dependence on the size of the outlet.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10675048 and 1068006
文摘Numerical simulations are employed to consider the problem of determining the granular temperatures of the species of a homogeneous heated granular mixture with a power-law size distribution. The partial granular temperature ratios are studied as functions of the fractal dimension D, the restitution coefflcient e, the rescaled viscosity time, the average occupied area fraction φ, the total particle number N and the number fraction. Different species of particles in a power-law system typically do not have the same mean kinetic energy, namely the granular temperature. It is found that the extent of nonequipartition of kinetic energy is determined by the fractal dimension D, the restitution coemcient e and the rescaled viscosity time, while is insensitive to the total particle number N, the area fraction φ and the number fraction.
文摘Granular materials exhibit abundant dissipations due to fluctuations in both granular motions and configurations （i.e., granular skeleton） evolutions. Twin granular temperatures Tk and T~ are introduced accounting for two types of fluctuations, and the so-called twin granular temperatures theory is established as an extension of granular solid hydrodynamics. By using simulations, the nonaffine deformations in a 2D assembly are simulated by using discrete element methods. By analogizing with microdamages in deformed solids, double scalar damage variables, Dp and Dq, are proposed to describe the deformed granular solid under triaxial compressions. Granular flows are found intrinsically turbulent due to the presence of Tk and the Naiver Stokes equation is obtained for granular flows.
基金supported by the European Commission Marie Curie Actions (IRSES-294976)
文摘Granular materials display more abundant dissipation phenomena than ordinary materials. In this paper, a brief energy flow path with irreversible processes is illustrated, where the concept of granular temperature Tg, initially proposed for dilute systems, is extended to dense systems in order to quantify disordered force chain configurations. Additionally, we develop the concept of conjugate granular entropy sg and its production equation. Our analyses find out that the granular entropy significantly undermined the elastic contact between particles, seriously affecting the transport coefficients in granular materials and creating new transport processes.
