The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibratio...The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.展开更多
In the present paper,a homogenization-based two-scale FEM-FEM model is developed to simulate compactions of visco-plastic granular assemblies.The granular structure consisting of two-dimensional grains is modeled by t...In the present paper,a homogenization-based two-scale FEM-FEM model is developed to simulate compactions of visco-plastic granular assemblies.The granular structure consisting of two-dimensional grains is modeled by the microscopic finite element method at the small-scale level,and the homogenized viscous assembly is analyzed by the macroscopic finite element method at large-scale level.The link between scales is made using a computational homogenization method.The two-scale FEM-FEM model is developed in which each particle is treated individually with the appropriate constitutive relations obtained from a representative volume element,kinematic conditions,contact constraints,and elimination of overlap satisfied for every particle.The method could be used in a variety of problems that can be represented using granular media.展开更多
The discrete element method(DEM)is a capable tool used to simulate shear wave propagation in granular assemblies for many years.Researchers have studied assembly shapes such as rectangles(in 2D simulations)or cylinder...The discrete element method(DEM)is a capable tool used to simulate shear wave propagation in granular assemblies for many years.Researchers have studied assembly shapes such as rectangles(in 2D simulations)or cylinders and cubes(in 3D simulations).This paper aimed to qualify the effect of assembly shape on the shear wave propagation and maximum amplification in the vertical plane(horizontal and vertical directions)caused by this propagation.To this end,shear wave propagations in different assembly shapes such as rectangle,trapezium,and triangle with rigid boundary conditions were simulated.A sine wave pulse was applied with a point source by moving a particle as the transmitter particle.To evaluate the shear wave velocity of the assemblies,the transmitter and receiver particles were simulated.All the simulations were performed with 2D DEM which is a useful tool to determine the amount and location of the maximum amplification factor of the assembly in both horizontal and vertical directions.An advantage of this study was assessing the effect of parameters such as input wave frequency,assembly height,shape,and aspect ratios on the amplification of the input waves.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51105092,61403106)International Science and Technology Cooperation Program of China(Grant No.2014DFR50250)the 111 Project,China(Grant No.B07018)
文摘The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.
基金This work was supported by National Natural Science Foundation of China(Grant No.10972162).
文摘In the present paper,a homogenization-based two-scale FEM-FEM model is developed to simulate compactions of visco-plastic granular assemblies.The granular structure consisting of two-dimensional grains is modeled by the microscopic finite element method at the small-scale level,and the homogenized viscous assembly is analyzed by the macroscopic finite element method at large-scale level.The link between scales is made using a computational homogenization method.The two-scale FEM-FEM model is developed in which each particle is treated individually with the appropriate constitutive relations obtained from a representative volume element,kinematic conditions,contact constraints,and elimination of overlap satisfied for every particle.The method could be used in a variety of problems that can be represented using granular media.
文摘The discrete element method(DEM)is a capable tool used to simulate shear wave propagation in granular assemblies for many years.Researchers have studied assembly shapes such as rectangles(in 2D simulations)or cylinders and cubes(in 3D simulations).This paper aimed to qualify the effect of assembly shape on the shear wave propagation and maximum amplification in the vertical plane(horizontal and vertical directions)caused by this propagation.To this end,shear wave propagations in different assembly shapes such as rectangle,trapezium,and triangle with rigid boundary conditions were simulated.A sine wave pulse was applied with a point source by moving a particle as the transmitter particle.To evaluate the shear wave velocity of the assemblies,the transmitter and receiver particles were simulated.All the simulations were performed with 2D DEM which is a useful tool to determine the amount and location of the maximum amplification factor of the assembly in both horizontal and vertical directions.An advantage of this study was assessing the effect of parameters such as input wave frequency,assembly height,shape,and aspect ratios on the amplification of the input waves.
