Apparent mass measurements at the bottom of silos have been carried out. An important parameter in the Janssen model known as the effective screening length has been investigated for different bead and silo diameters ...Apparent mass measurements at the bottom of silos have been carried out. An important parameter in the Janssen model known as the effective screening length has been investigated for different bead and silo diameters as well as of their ratios. It is found that the effective screening length augments with the grain diameter d in addition to the granular column size. It is also revealed that λ exhibits stronger correlation with the bead diameter than that of the silo. This phenomenon is attributed to the reduced-shielding of the vertical stresses to the horizontal ones.展开更多
Fluid-particle interaction underpins important behavior of granular media. Particle-scale simulation may help to provide key microscopic information governing the interaction and offer better understanding of granular...Fluid-particle interaction underpins important behavior of granular media. Particle-scale simulation may help to provide key microscopic information governing the interaction and offer better understanding of granular media as a whole. This paper presents a coupled computational fluid dynamics and discrete element method （CFD-DEM） approach for this purpose. The granular particle system is modeled by DEM, while the fluid flow is simulated by solving the locally averaged Navier-Stokes equation with CFD. The coupling is considered by exchanging such interaction forces as drag force and buoyancy force between the DEM and CFD. The approach is benchmarked by two classic geomechanics problems for which analytical solutions are available, and is further applied to the prediction of sand heap formation in water through hopper flow. It is demonstrated that the key characteristic of granular materials interacting with pore water can be successfully captured by the proposed method.展开更多
Storage of iron ore pellet feed fines (with 90% minimum granulometry of <45 μm and 100% <150 micron) can be studied through the mechanics of granular materials. Geotechnical inputs are not able to explain the f...Storage of iron ore pellet feed fines (with 90% minimum granulometry of <45 μm and 100% <150 micron) can be studied through the mechanics of granular materials. Geotechnical inputs are not able to explain the failure phenomenon comprehensively. Yet, in the industry the trend is to work with geotechnical inputs and an exaggerated degree of visual interpretation. The first part of this article briefly shows some articles in which authors emphasize the mechanics of granular materials and an article placing emphasis on the geotechnical features of granular materials. The second part shows the solution to the equation developed by [1] applied to the geometry of iron ore storage piles. The scale model study of stress variation on the model’s axis is done and the comparison of the stress variation and Thamwattana’s analytical resolution is commented. The third part shows a stress distribution study formulating centered finite differences by applying the Itasca Consulting Group’s PFC2D software to the iron ore stockpile within the same footprint as the stockpile in the analytical model. This study’s conclusions are as follows: 1) The differential between the models is the differences between tangential and normal rigidity. These differences between tangential rigidity Kt and normal rigidity Kn make the stockpile unstable. We can state that when Kn = Kt the stockpiles are more stable. 2) The models and all the work done show that the stockpiles are not stable. The stockpiles are at times temporarily stable, but even after formation, these stockpiles are unstable and the particles are always moving.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10675018 and 10674157)the Department of Electrical Engineering,Sukkur Institute of Business Administration, Sukkur, Sindh, Pakistan
文摘Apparent mass measurements at the bottom of silos have been carried out. An important parameter in the Janssen model known as the effective screening length has been investigated for different bead and silo diameters as well as of their ratios. It is found that the effective screening length augments with the grain diameter d in addition to the granular column size. It is also revealed that λ exhibits stronger correlation with the bead diameter than that of the silo. This phenomenon is attributed to the reduced-shielding of the vertical stresses to the horizontal ones.
基金supported by the Research Grants Council of Hong Kong (622910)
文摘Fluid-particle interaction underpins important behavior of granular media. Particle-scale simulation may help to provide key microscopic information governing the interaction and offer better understanding of granular media as a whole. This paper presents a coupled computational fluid dynamics and discrete element method （CFD-DEM） approach for this purpose. The granular particle system is modeled by DEM, while the fluid flow is simulated by solving the locally averaged Navier-Stokes equation with CFD. The coupling is considered by exchanging such interaction forces as drag force and buoyancy force between the DEM and CFD. The approach is benchmarked by two classic geomechanics problems for which analytical solutions are available, and is further applied to the prediction of sand heap formation in water through hopper flow. It is demonstrated that the key characteristic of granular materials interacting with pore water can be successfully captured by the proposed method.
文摘Storage of iron ore pellet feed fines (with 90% minimum granulometry of <45 μm and 100% <150 micron) can be studied through the mechanics of granular materials. Geotechnical inputs are not able to explain the failure phenomenon comprehensively. Yet, in the industry the trend is to work with geotechnical inputs and an exaggerated degree of visual interpretation. The first part of this article briefly shows some articles in which authors emphasize the mechanics of granular materials and an article placing emphasis on the geotechnical features of granular materials. The second part shows the solution to the equation developed by [1] applied to the geometry of iron ore storage piles. The scale model study of stress variation on the model’s axis is done and the comparison of the stress variation and Thamwattana’s analytical resolution is commented. The third part shows a stress distribution study formulating centered finite differences by applying the Itasca Consulting Group’s PFC2D software to the iron ore stockpile within the same footprint as the stockpile in the analytical model. This study’s conclusions are as follows: 1) The differential between the models is the differences between tangential and normal rigidity. These differences between tangential rigidity Kt and normal rigidity Kn make the stockpile unstable. We can state that when Kn = Kt the stockpiles are more stable. 2) The models and all the work done show that the stockpiles are not stable. The stockpiles are at times temporarily stable, but even after formation, these stockpiles are unstable and the particles are always moving.
