We employ a Hall-effect magnetic sensor array to accurately track the trajectory of a single magnetic sphere,referred to as the“intruder,”within a three-dimensional vibro-fluidized granular bed to unravel the underl...We employ a Hall-effect magnetic sensor array to accurately track the trajectory of a single magnetic sphere,referred to as the“intruder,”within a three-dimensional vibro-fluidized granular bed to unravel the underlying physical mechanism governing the motion of the intruder.Within the acceleration range of 3.5 g≥Γ≥1.5 g,we find that,regardless of the intruder's initial position,it consistently reaches the same equilibrium depth when the vibration acceleration(Γ)and frequency(ω)are fixed.ForΓ≤2.5 g,the equilibrium position lies on the surface of the granular bed,while forΓ>2.5 g,it shifts below the surface.Additionally,intruders with different densities exhibit varying equilibrium depths,with higher density resulting in a deeper equilibrium position.To understand the mechanism behind the intruder's upward or downward motion,we measure its rising or sinking velocities under different vibration parameters.Our findings demonstrate that the rising velocity of the intruder,under varying vibration accelerations(Γ)and frequencies(ω),can be collapsed using the ratioΓ/ω,while the sinking velocity remains unaffected by the vibration strength.This confirms that the upward motion of the larger sphere,associated with the Brazil nut effect,primarily arises from the void-filling mechanism of the bed particles.Furthermore,our experiments reveal that the presence of convection within the bed particles has minimal impact on the motion of the intruder.展开更多
在有一样的尺寸的垂直地二进制的小粒的混合物的分离试验性地被学习。一个新部分分离状态在系统被发现。这个状态在完全混合的状态和纯分离状态之间存在并且有更轻的粒子趋于升起并且当更轻的更重的粒子和一些呆在底部并且形成混合的层...在有一样的尺寸的垂直地二进制的小粒的混合物的分离试验性地被学习。一个新部分分离状态在系统被发现。这个状态在完全混合的状态和纯分离状态之间存在并且有更轻的粒子趋于升起并且当更轻的更重的粒子和一些呆在底部并且形成混合的层时，在系统的顶上形成纯层的特征。纯最高的层和整个系统的厚度的比率与颤动频率或振幅连续地变化。把比率看作一个顺序参数被建议，一张详细阶段图在 Gamma 诗句 f 空间被获得。最后，观察部分分离状态的形成被在更重的粒子的动量的影响之间的比赛说明，层的僵硬混合粒子创作了。展开更多
Energy dissipation is one of the most important properties of granular gas, which makes Its behavior dltterent trom that of molecular gas. In this work we report our investigations on the freely-cooling evolution of g...Energy dissipation is one of the most important properties of granular gas, which makes Its behavior dltterent trom that of molecular gas. In this work we report our investigations on the freely-cooling evolution of granular gas under microgravity in a drop tower experiment, and also conduct the molecular dynamics （MD） simulation for comparison. While our experimental and simulation results support Haff＇s law that the kinetic energy dissipates with time t as E（t） （1 ＋ t/v） 2, we modify ~＂ by taking into account the friction dissipation during collisions, and study the effects of number density and particle size on the collision frequency. From the standard deviation of the measured velocity distributions we also verify the energy dissipation law, which is in agreement with Haff＇s kinetic energy dissipation.展开更多
In this paper,granular segregation in a two-compartment cell in zero gravity is studied numerically by DEM simulation.In the simulation using a virtual window method we find a non-monotonic flux,a function which gover...In this paper,granular segregation in a two-compartment cell in zero gravity is studied numerically by DEM simulation.In the simulation using a virtual window method we find a non-monotonic flux,a function which governs the segregation.A parameter is used to quantify the segregation.The effect of three parameters：the total number of particles N,the excitation strength F,and the position of the window coupling the two compartments,on the segregation and the waiting time%are investigated.It is found that the segregation observed in zero gravity exists and does not depend on the excitation strength F.The waiting time T,however,depends strongly on F：the higher the F,the lower the waiting time V,The simulation results are important in guiding the SJ-10 satellite microgravity experiments.展开更多
The axial-stress dependence of sound wave velocity in granular packing is experimentally investigated with tri-axial and uni-axial devices. Preparing samples by repetitive loadings and unloadings in a range of 20 kPa...The axial-stress dependence of sound wave velocity in granular packing is experimentally investigated with tri-axial and uni-axial devices. Preparing samples by repetitive loadings and unloadings in a range of 20 kPa–1000 kPa, we find that the axial-stress dependence of sound wave velocity approaches the Hertz scaling with an exponent of 1/6 for large axial stresses（〉 400 kPa）. Weak deviation from the Hertz scaling is seen at low stresses. Repetitive axial loadings slightly reduce this deviation, and sound velocities increase nonlinearly approaching some saturated values. Velocities for uni-axial case are found slightly to be bigger than those for tri-axial isotropic compression case. These effects are discussed in the frameworks of granular solid hydrodynamics（GSH） and effective medium theory（EMT）, which indicate that they cannot be explained with density nor Janssen ratio only. Dissipation occurring during wave propagation may be a non-negligible factor.展开更多
基金Project supported by the Space Application System of China Manned Space Programthe National Natural Science Foundation of China(Grant Nos.12072200 and 12002213)。
文摘We employ a Hall-effect magnetic sensor array to accurately track the trajectory of a single magnetic sphere,referred to as the“intruder,”within a three-dimensional vibro-fluidized granular bed to unravel the underlying physical mechanism governing the motion of the intruder.Within the acceleration range of 3.5 g≥Γ≥1.5 g,we find that,regardless of the intruder's initial position,it consistently reaches the same equilibrium depth when the vibration acceleration(Γ)and frequency(ω)are fixed.ForΓ≤2.5 g,the equilibrium position lies on the surface of the granular bed,while forΓ>2.5 g,it shifts below the surface.Additionally,intruders with different densities exhibit varying equilibrium depths,with higher density resulting in a deeper equilibrium position.To understand the mechanism behind the intruder's upward or downward motion,we measure its rising or sinking velocities under different vibration parameters.Our findings demonstrate that the rising velocity of the intruder,under varying vibration accelerations(Γ)and frequencies(ω),can be collapsed using the ratioΓ/ω,while the sinking velocity remains unaffected by the vibration strength.This confirms that the upward motion of the larger sphere,associated with the Brazil nut effect,primarily arises from the void-filling mechanism of the bed particles.Furthermore,our experiments reveal that the presence of convection within the bed particles has minimal impact on the motion of the intruder.
基金Supported by the National Key Programme for Basic Research of China, and the National Science Foundation of China under Grant No 10374111.
文摘在有一样的尺寸的垂直地二进制的小粒的混合物的分离试验性地被学习。一个新部分分离状态在系统被发现。这个状态在完全混合的状态和纯分离状态之间存在并且有更轻的粒子趋于升起并且当更轻的更重的粒子和一些呆在底部并且形成混合的层时，在系统的顶上形成纯层的特征。纯最高的层和整个系统的厚度的比率与颤动频率或振幅连续地变化。把比率看作一个顺序参数被建议，一张详细阶段图在 Gamma 诗句 f 空间被获得。最后，观察部分分离状态的形成被在更重的粒子的动量的影响之间的比赛说明，层的僵硬混合粒子创作了。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1738120 and 11474326)
文摘Energy dissipation is one of the most important properties of granular gas, which makes Its behavior dltterent trom that of molecular gas. In this work we report our investigations on the freely-cooling evolution of granular gas under microgravity in a drop tower experiment, and also conduct the molecular dynamics （MD） simulation for comparison. While our experimental and simulation results support Haff＇s law that the kinetic energy dissipates with time t as E（t） （1 ＋ t/v） 2, we modify ~＂ by taking into account the friction dissipation during collisions, and study the effects of number density and particle size on the collision frequency. From the standard deviation of the measured velocity distributions we also verify the energy dissipation law, which is in agreement with Haff＇s kinetic energy dissipation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474326 and 11274354)the "Strategic Priority Research Program-SJ-10" of the Chinese Academy of Sciences(Grant No.XDA04020200)the Special Fund for Earthquake Research of China(Grant No.201208011)
文摘In this paper,granular segregation in a two-compartment cell in zero gravity is studied numerically by DEM simulation.In the simulation using a virtual window method we find a non-monotonic flux,a function which governs the segregation.A parameter is used to quantify the segregation.The effect of three parameters：the total number of particles N,the excitation strength F,and the position of the window coupling the two compartments,on the segregation and the waiting time%are investigated.It is found that the segregation observed in zero gravity exists and does not depend on the excitation strength F.The waiting time T,however,depends strongly on F：the higher the F,the lower the waiting time V,The simulation results are important in guiding the SJ-10 satellite microgravity experiments.
基金supported by the National Natural Science Foundation of China(Grant Nos.11274354 and11474326)the Strategic Priority Research Program-SJ-10 of the Chinese Academy of Sciences(Grant No.XDA04020200)
文摘The axial-stress dependence of sound wave velocity in granular packing is experimentally investigated with tri-axial and uni-axial devices. Preparing samples by repetitive loadings and unloadings in a range of 20 kPa–1000 kPa, we find that the axial-stress dependence of sound wave velocity approaches the Hertz scaling with an exponent of 1/6 for large axial stresses（〉 400 kPa）. Weak deviation from the Hertz scaling is seen at low stresses. Repetitive axial loadings slightly reduce this deviation, and sound velocities increase nonlinearly approaching some saturated values. Velocities for uni-axial case are found slightly to be bigger than those for tri-axial isotropic compression case. These effects are discussed in the frameworks of granular solid hydrodynamics（GSH） and effective medium theory（EMT）, which indicate that they cannot be explained with density nor Janssen ratio only. Dissipation occurring during wave propagation may be a non-negligible factor.
