A discrete element model based on super-ellipsoids was used to simulate cylindrical particle flow. The model can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to...A discrete element model based on super-ellipsoids was used to simulate cylindrical particle flow. The model can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to appropriate values. To achieve more rapid calculations, we implemented an "oriented bounding box algorithm"(OBBA) for the initial contact detection of cylindrical particles. Several types of Simulations were performed to validate the super-ellipsoid model and the contact-detection algorithm. First, the effect of shape index of the super-ellipsoids on model accuracy was investigated through three simulations: impact of a cylindrical particle on a flat wall, flow of cylindrical particles in a rotating tumbler, and segregation of cylindrical particles of different length flowing down a bounded heap. The simulation results show that the super-ellipsoids describe cylindrical particles accurately when the shape index that specifies the sharpness of the cylinder edges is sufficiently large. The efficiency of the OBBA is measured by simulations in which a box is filled with cylindrical particles and a tumbler that contains cylindrical particles is rotated. The simulation results show that the OBBA can accelerate the calculations significantly. The effect of particle shape (such as aspect ratio and shape index) on the calculation speed was obtained. The simulation of rod-like particles tended to take more calculation time than that of disk-like particles, and the simulation time increased with an increasing particle-shape index.展开更多
Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials.And substantial efforts have been dev...Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials.And substantial efforts have been devoted to the study of the screw conveyors.Numerical method is an effective way to study screw conveyor.However,previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still limited.In view of the above situations,discrete element method(DEM),which has been widely accepted in simulating the discrete systems,is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor,with particles being modeled by super-ellipsoids.In addition,a wear model called SIEM(Shear Impact Energy Model)is incorporated into DEM to predict the wear of screw conveyor.The DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of conveyor.The conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation parameters.Moreover,particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw blade.The comparisons between particle-particle collision and particle-wall collision reveal that particles with large shape index have more possibility to be damaged in particle-wall impingement.展开更多
In industrial blast furnaces(BFs),the investigations involving the flow behaviors of particles and the resultant burden structure are essential to optimize its operation stability and energy consumption.With the advan...In industrial blast furnaces(BFs),the investigations involving the flow behaviors of particles and the resultant burden structure are essential to optimize its operation stability and energy consumption.With the advance of computing capability and mathematical model,the discrete element method(DEM)specialized in characterizing particle behavior has manifested its power in the investigation of BFs.In the framework of DEM,many particle models have been developed,but which model is more suitable for simulating the particle behaviors of BFs remains a question because real particles in BFs have large shape and size dispersity.Among these particle models,the super-ellipsoid model possesses the ability to change shape flexibly.Therefore,the focus of this study is to investigate whether the super-ellipsoid model can meet the requirement of authenticity and accuracy in simulating the behaviors of particles with large shape and size dispersity.To answer this question,a simplified BF charging system composed of a hopper and a storage bin is established.The charging process and the final packing structure are analyzed and compared between experiments and simulations with different shape indexes.The results show that super-ellipsoid particles have prominent advantages over spherical particles in terms of representing the real BF particles,and it can more reasonably reproduce the flow behaviors and packing structure of experimental particles.The computation cost of super-ellipsoid particles is also acceptable for engineering applications.Finally,the micro-scale characteristics of packing structure is analyzed and the single-ring charging process in industry-scale BF using super-ellipsoid particles is conducted.展开更多
采用OPAC(Optical Properties of Aerosols and Clouds)模型提供的沙尘粒子谱分布和复折射率参数,结合多个入射波长,对群体沙尘气溶胶粒子的退偏振比进行了数值模拟计算。计算获得1064 nm、532 nm和355 nm入射波长下,不同轴比超椭球模...采用OPAC(Optical Properties of Aerosols and Clouds)模型提供的沙尘粒子谱分布和复折射率参数,结合多个入射波长,对群体沙尘气溶胶粒子的退偏振比进行了数值模拟计算。计算获得1064 nm、532 nm和355 nm入射波长下,不同轴比超椭球模型的沙尘气溶胶粒子群体的退偏振比分别为0.317,0.397和0.446,其中1064 nm波长的仿真结果与实际观测结果一致性最好,其次是532 nm波长的仿真结果,355 nm波长的仿真结果和实际观测结果有较大差异,其可能原因为采用了相同数目偶极子导致计算误差增大。本仿真研究中建立的非球形粒子散射模型和数值计算方法,为深入理解沙尘气溶胶光散射特性和研制多波长偏振激光雷达提供了理论基础。同时,多波长偏振探测也为气溶胶混合态和污染型气溶胶生成机理研究提供了重要的技术手段。展开更多
基金the China Scholarship Council and the National Natural Science Foundation of China (NSFC, Grant No. 51741608)thanks Austin Isner for help with data processing. The authors thank Guillaume Adoneth and Quentin Mougeot for acquiring experimental data on the seg-regation of cylindrical particles in a quasi-2D bounded heap.
文摘A discrete element model based on super-ellipsoids was used to simulate cylindrical particle flow. The model can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to appropriate values. To achieve more rapid calculations, we implemented an "oriented bounding box algorithm"(OBBA) for the initial contact detection of cylindrical particles. Several types of Simulations were performed to validate the super-ellipsoid model and the contact-detection algorithm. First, the effect of shape index of the super-ellipsoids on model accuracy was investigated through three simulations: impact of a cylindrical particle on a flat wall, flow of cylindrical particles in a rotating tumbler, and segregation of cylindrical particles of different length flowing down a bounded heap. The simulation results show that the super-ellipsoids describe cylindrical particles accurately when the shape index that specifies the sharpness of the cylinder edges is sufficiently large. The efficiency of the OBBA is measured by simulations in which a box is filled with cylindrical particles and a tumbler that contains cylindrical particles is rotated. The simulation results show that the OBBA can accelerate the calculations significantly. The effect of particle shape (such as aspect ratio and shape index) on the calculation speed was obtained. The simulation of rod-like particles tended to take more calculation time than that of disk-like particles, and the simulation time increased with an increasing particle-shape index.
基金This research was financially supported by the National Key Research and Development Program of China(grant No.2019YFC1805605)the National Natural Science Foundation of China(grant No.22078283)。
文摘Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials.And substantial efforts have been devoted to the study of the screw conveyors.Numerical method is an effective way to study screw conveyor.However,previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still limited.In view of the above situations,discrete element method(DEM),which has been widely accepted in simulating the discrete systems,is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor,with particles being modeled by super-ellipsoids.In addition,a wear model called SIEM(Shear Impact Energy Model)is incorporated into DEM to predict the wear of screw conveyor.The DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of conveyor.The conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation parameters.Moreover,particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw blade.The comparisons between particle-particle collision and particle-wall collision reveal that particles with large shape index have more possibility to be damaged in particle-wall impingement.
基金This researchwas financially supported by the National Natural Science Foundation of China(grant No.22078283).
文摘In industrial blast furnaces(BFs),the investigations involving the flow behaviors of particles and the resultant burden structure are essential to optimize its operation stability and energy consumption.With the advance of computing capability and mathematical model,the discrete element method(DEM)specialized in characterizing particle behavior has manifested its power in the investigation of BFs.In the framework of DEM,many particle models have been developed,but which model is more suitable for simulating the particle behaviors of BFs remains a question because real particles in BFs have large shape and size dispersity.Among these particle models,the super-ellipsoid model possesses the ability to change shape flexibly.Therefore,the focus of this study is to investigate whether the super-ellipsoid model can meet the requirement of authenticity and accuracy in simulating the behaviors of particles with large shape and size dispersity.To answer this question,a simplified BF charging system composed of a hopper and a storage bin is established.The charging process and the final packing structure are analyzed and compared between experiments and simulations with different shape indexes.The results show that super-ellipsoid particles have prominent advantages over spherical particles in terms of representing the real BF particles,and it can more reasonably reproduce the flow behaviors and packing structure of experimental particles.The computation cost of super-ellipsoid particles is also acceptable for engineering applications.Finally,the micro-scale characteristics of packing structure is analyzed and the single-ring charging process in industry-scale BF using super-ellipsoid particles is conducted.
