Tangential Force Model for the Combined Finite-Discrete Element Method

2019 ◽  
Vol 17 (09) ◽  
pp. 1950068
Author(s):  
Xunnan Liu ◽  
Lanhao Zhao ◽  
Jia Mao ◽  
Tongchun Li
Keyword(s):  
Discrete Element Method ◽  
Contact Interaction ◽  
Contact Force ◽  
Tangential Force ◽  
Numerical Test ◽  
Discrete Element ◽  
Force Model ◽  
Normal Contact ◽  
Tangential Contact ◽  
Element Method

In the past, contact model in the combined finite-discrete element method (FDEM) does not include the influence of the tangential contact interaction, and the deficient model associated with the contact force can seriously degrade the computing accuracy. In order to overcome this defect, an improved FDEM is developed in this work. The potential contact mechanism is implemented to calculate the normal contact force; meanwhile, the force-displacement law by coupling the classical Mohr–Coulomb type frictional algorithm and the rotation transformation algorithm is applied for the accurate computation of the tangential contact force. Consequently, a holonomic system of the calculation algorithm for the contact interaction is proposed, accounting for the influence of the tangential contact force. The performance of the approach is validated with well-known benchmarks including a frictional numerical test, the dynamic response of the block under the seismic excitation, a sliding/toppling test of a joint rock slope, a numerical simulation for joints structure affecting a sliding rock mass and the 2008 Donghekou Landslide trigged by the Wenchuan Earthquake. The results are compared against the experimental data and analytical solutions. Excellent agreements between the computational result and existing measurements show that the proposed approach has an outstanding ability to describe the complex mechanical properties among the separate entities.

scholarly journals Computer Aided Modeling of Wood Chips Transport by Means of a Belt Conveyor with Use of Discrete Element Method

2020 ◽  
Vol 10 (24) ◽  
pp. 9091
Author(s):  
Łukasz Gierz ◽  
Łukasz Warguła ◽  
Mateusz Kukla ◽  
Krzysztof Koszela ◽  
Tomasz Szymon Zwiachel
Keyword(s):  
Discrete Element Method ◽  
Analytical Model ◽  
Inclination Angle ◽  
Numerical Test ◽  
Discrete Element ◽  
Conveyor Belt ◽  
Wood Chips ◽  
Belt Conveyor ◽  
Belt Speed ◽  
Element Method

The effectiveness and precision of transporting wood chips on the transport trailer or hopper depends on an inclination angle, a conveyor belt speed, and length. In order to devise a methodology aiding designing and the selection of technical and performance parameters (aiding the settings of conveyor belt sub-assemblies), the authors carried out the simulation tests concerning wood chips transport on the belt conveyor and their outlet. For the purposes of these tests, a simulation model was performed in the Rocky DEM (discrete element method) software in the numerical analysis environment and compared to analytical tests. The tested wood chips were taken from cherry plum branches chipping processes (Prunus cerasifera Ehrh. Beitr. Naturk. 4:17. 1789 (Gartenkalender 4:189-204. 1784)), out of which seven basic fractions were separated, which differed mainly in terms of their diameter from 5 mm to 50 mm and the length of 150 mm. The article presents the results of wood chips ejection distance in the form of the 3D functions of wood chips ejection distance depending on the conveyor belt inclination angle and belt speed. The results are presented for five conveyor belt lengths (1 m, 2 m, 3 m, 4 m, 5 m). The tests also involved the conveyor belt inclination angle in the range from 10° to 50° and the belt velocity in the range from 1 m/s2 to 5 m/s2. The numerical test results demonstrate higher average values of wood chips ejection distance than designated in the analytical model. The average arithmetical difference in the results between the numerical and analytical model is at the level of 13%.

Simulation of Pressing Effect of Press Wheel with Different Rims by Discrete Element Method

2011 ◽  
Vol 101-102 ◽  
pp. 551-555
Author(s):  
Fu Lan Wang ◽  
Hong Lei Jia ◽  
Dan Dan Liu
Keyword(s):  
Discrete Element Method ◽  
Contact Force ◽  
Discrete Element ◽  
Soil Displacement ◽  
The Press ◽  
Better Than ◽  
Element Method

Pressing is an important part of precision seeding operation, which has an important effect on crushing soil. In order to enhancing the effect of soil crushing, some press wheels with flange rim are used. But further research is needed to evaluate whether the use of these press wheels affect the actual seeding depth that will affect precision seeding quality. Three kinds of press wheels, with the smooth rim, circular flange rim and rib rim respectively were designed, and the PFC3D discrete element method (DEM) software was used to simulate the pressing processes of these press wheels, and the contact force between the rim and soil, soil displacement and porosity were analyzed. It was concluded that the press wheel with the smooth rim is better than others in precision seeding operation.

scholarly journals A Dynamic Coarse Grain Discrete Element Method for Gas-Solid Fluidized Beds by Considering Particle-Group Crushing and Polymerization

2020 ◽  
Vol 10 (6) ◽  
pp. 1943
Author(s):  
Xiaodong Wang ◽  
Kai Chen ◽  
Ting Kang ◽  
Jie Ouyang
Keyword(s):  
Discrete Element Method ◽  
Fluidized Beds ◽  
Stokes Equations ◽  
Discrete Element ◽  
Coarse Grain ◽  
Equivalent Diameter ◽  
Force Model ◽  
Simpler Algorithm ◽  
Particle Group ◽  
Element Method

The discrete element method (DEM) coupled with computational fluid dynamics (CFD) is used extensively for the numerical simulation of gas-solid fluidized beds. In order to improve the efficiency of this approach, a coarse grain model of the DEM was proposed in the literature. In this model, a group of original particles are treated as a large-sized particle based on the initial particle distribution, and during the whole simulation process the number and components of these particle-groups remain unchanged. However, collisions between particles can lead to frequent crushing and polymerization of particle-groups. This fact has typically been ignored, so the purpose of this paper is to rationalize the coarse grain DEM-CFD model by considering the dynamic particle-group crushing and polymerization. In particular, the effective size of each particle-group is measured by a quantity called equivalent particle-group diameter, whose definition references the equivalent cluster diameter used by the energy-minimization multi-scale (EMMS) model. Then a particle-group crushing criterion is presented based on the mismatch between the equivalent diameter and actual diameter of a particle-group. As to the polymerization of two colliding particle-groups, their velocity difference after collision is chosen as a criterion. Moreover, considering the flow heterogeneity induced by the particle cluster formation, the EMMS drag force model is adopted in this work. Simulations are carried out by using a finite volume method (FVM) with non-staggered grids. For decoupling the Navier-Stokes equations, the semi-implicit method for pressure linked equations revised (SIMPLER) algorithm is used. The simulation results show that the proposed dynamic coarse grain DEM-CFD method has better performance than the original one.

scholarly journals Inclined model experiment and discrete element method simulation of reinforced soil wall with leakage of backfill material

2019 ◽  
Vol 92 ◽  
pp. 17005
Author(s):  
Takehiko Nitta ◽  
Hiroaki Miyatake ◽  
Toshikazu Sawamatsu ◽  
Tomohiro Fujita ◽  
Noboru Sato ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Tensile Force ◽  
Discrete Element ◽  
Reinforced Soil ◽  
Contact Forces ◽  
Normal Contact ◽  
Model Experiments ◽  
Backfill Material ◽  
Reinforced Soil Wall ◽  
Element Method

In this study, a series of inclined model experiments were conducted to investigate the behaviour of reinforced soil walls with leakage of backfill material. The experimental results were simulated by discrete element method (DEM). From the results of the inclined model experiments, it was confirmed that the tensile force in the reinforcement near the wall facing decreased due to the leakage of the backfill material, while decreasing the horizontal resistance of the reinforced soil wall remarkably. The leakage behaviour observed in the experiment was simulated using DEM. From the results of the DEM simulation, the calculated displacement pattern was found to be roughly similar to that obtained in the experiment. During leakage of the backfill material, an area without normal contact forces was generated at the lower end and this area developed toward the upper side. Such a change in normal contact forces affects the behaviour of a geogrid, in particular the disappearance of normal contact forces weakens the interlocking between the geogrid and the soil. This observation agrees with the experimental finding that the strain of the geogrid decreased in the area near the back of the wall facing.

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