以水平回转式干馏炉为研究对象,采用离散单元法(discrete element method,DEM)建立颗粒运动模型,接触模型采用Hertz无滑动接触模型,分别对在其内设置不同形式抄板(直角抄板﹑弯抄板和直抄板)的混合效果和混合规律进行了数值研究。将大...以水平回转式干馏炉为研究对象,采用离散单元法(discrete element method,DEM)建立颗粒运动模型,接触模型采用Hertz无滑动接触模型,分别对在其内设置不同形式抄板(直角抄板﹑弯抄板和直抄板)的混合效果和混合规律进行了数值研究。将大小颗粒间接触数与颗粒间接触总数之比定义为混合质量,并以此来衡量混合程度,同时分析抄板形式及转速对混合质量的影响。研究结果表明,干馏炉内设抄板时,混合趋于稳定的时间较短,抄板形式对混合质量的影响较小;随着转速的降低,混合质量曲线越平缓,波动幅度越小。研究结果对干馏炉的设计和优化具有一定的指导作用。展开更多
City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation,affecting the surface environment and the safety of the tunnels.Due to its strong dis...City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation,affecting the surface environment and the safety of the tunnels.Due to its strong dispersion,sandy cobble strata can be easily disturbed by shield tunneling.Based on the project of the Chengdu Metro Line 1,field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves,ground loss ratios and construction influence zones.The discrete element method(DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level.Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil.The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.展开更多
Both linear-spring-dashpot （LSD） and non-linear Hertzian-spring-dashpot （HSD） contact models are commonly used for the calculation of contact forces in Discrete Element Method （DEM） simulations of granular syste...Both linear-spring-dashpot （LSD） and non-linear Hertzian-spring-dashpot （HSD） contact models are commonly used for the calculation of contact forces in Discrete Element Method （DEM） simulations of granular systems. Despite the popularity of these models, determination of suitable values for the contact parameters of the simulated particles such as stiffness, damping coefficient, coefficient of restitution, and simulation time step, is not altogether obvious. In this work the relationships between these contact parameters for a model system where a particle impacts on a flat base are examined. Recommendations are made concerning the determination of these contact parameters for use in DEM simulations.展开更多
文摘以水平回转式干馏炉为研究对象,采用离散单元法(discrete element method,DEM)建立颗粒运动模型,接触模型采用Hertz无滑动接触模型,分别对在其内设置不同形式抄板(直角抄板﹑弯抄板和直抄板)的混合效果和混合规律进行了数值研究。将大小颗粒间接触数与颗粒间接触总数之比定义为混合质量,并以此来衡量混合程度,同时分析抄板形式及转速对混合质量的影响。研究结果表明,干馏炉内设抄板时,混合趋于稳定的时间较短,抄板形式对混合质量的影响较小;随着转速的降低,混合质量曲线越平缓,波动幅度越小。研究结果对干馏炉的设计和优化具有一定的指导作用。
基金Project supported by the National Basic Research (973) Program of China (No. 2010CB732105)the National Natural Science Foundation of China (Nos. 50908193,50925830,and 51208432)
文摘City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation,affecting the surface environment and the safety of the tunnels.Due to its strong dispersion,sandy cobble strata can be easily disturbed by shield tunneling.Based on the project of the Chengdu Metro Line 1,field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves,ground loss ratios and construction influence zones.The discrete element method(DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level.Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil.The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.
基金support to Mr Malone in the form of CASE studentship [GR/P03711/01].
文摘Both linear-spring-dashpot （LSD） and non-linear Hertzian-spring-dashpot （HSD） contact models are commonly used for the calculation of contact forces in Discrete Element Method （DEM） simulations of granular systems. Despite the popularity of these models, determination of suitable values for the contact parameters of the simulated particles such as stiffness, damping coefficient, coefficient of restitution, and simulation time step, is not altogether obvious. In this work the relationships between these contact parameters for a model system where a particle impacts on a flat base are examined. Recommendations are made concerning the determination of these contact parameters for use in DEM simulations.
