Periodic boundary conditions of discrete element method-lattice Boltzmann method for fluid-particle coupling

Num Anal Meth Geomechanics

Pande

et al. 2018

Self Cite

Summary This paper presents a 3D bonded discrete element and lattice Boltzmann method for resolving the fluid‐solid interaction involving complicated fluid‐particle coupling in geomaterials. In the coupled technique, the solid material is treated as an assembly of bonded and/or granular particles. A bond model accounting for strain softening in normal contact is incorporated into the discrete element method to simulate the mechanical behaviour of geomaterials, whilst the fluid flow is solved by the lattice Boltzmann method based on kinetic theory and statistical mechanics. To provide a bridge between theory and application, a 3D algorithm of immersed moving boundary scheme was proposed for resolving fluid‐particle interaction. To demonstrate the applicability and accuracy of this coupled method, a benchmark called quicksand, in which particles become fluidised under the driving of upward fluid flow, is first carried out. The critical hydraulic gradient obtained from the numerical results matches the theoretical value. Then, numerical investigation of the performance of granular filters generated according to the well‐acknowledged design criteria is given. It is found that the proposed 3D technique is promising, and the instantaneous migration of the protected soils can be readily observed. Numerical results prove that the filters which comply with the design criteria can effectively alleviate or eliminate the appearance of particle erosion in dams.

Section: Computational Methodologymentioning

confidence: 99%

“…Although there have been lots of papers on the theory and application of IMB, its implementation is seldom reported. 61 The detailed procedures are given below.…”

Section: Algorithm Of Imbmentioning

confidence: 99%

A coupled 3‐dimensional bonded discrete element and lattice Boltzmann method for fluid‐solid coupling in cohesive geomaterials

Num Anal Meth Geomechanics

Pande

et al. 2018

Self Cite

“…The computational costs of IBM and IMB in different tests are given in Table . It should be mentioned that in the above simulations by IMB, the searching algorithm and the method for computing nodal solid ratio are the same as those used in our previous work . A more efficient algorithm can be found in our latest work …”

Section: Discussionmentioning

confidence: 99%

“…Detailed development of the coupling schemes used in DEM‐LBM was introduced in our previous work . Applications of this hybrid technique in hydraulic fracture, sand production, soil erosion, liquefaction, and other problems can be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

On the implicit immersed boundary method in coupled discrete element and lattice Boltzmann method

Num Anal Meth Geomechanics

2019

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The coupled discrete element method and lattice Boltzmann method (DEMLBM) has increasingly drawn attention of researchers in geomechanics due to its mesoscopic nature since 2000. Immersed boundary method (IBM) and immersed moving boundary (IMB) are two popular schemes for coupling fluid particle in DEMLBM. This work aims at coupling DEM and LBM using the latest IBM algorithm and investigating its accuracy, computational efficiency, and applicability. Two benchmark tests, interstitial fluid flow in an ideal packing and single particle sedimentation in viscous fluid, are carried out to demonstrate the accuracy of IBM through semi-empirical Ergun equation, finite element method (FEM), and IMB. Then, simulations of particle migration with relatively large velocity in Poiseuille flow are utilized to address limitations of IBM in DEMLBM modeling. In addition, advantages and deficiencies of IBM are discussed and compared with IMB. It is found that the accuracy of IBM can be only guaranteed when sufficient boundary points are used and it is not suitable for geomechanical problems involving large fluid or particle velocity.discrete element method, fluid-solid interaction, immersed boundary method, immersed moving boundary, lattice Boltzmann method | INTRODUCTIONThe fluid-solid interaction (FSI) is frequently encountered in geotechnical engineering. Its complexity stems from the interaction between pore fluid and grains which consist of geomaterials like soil and rock. Liquefaction, soil erosion, and sand production are typical geomechanical problems which involve strong pore fluid-particle coupling. However, microscopic investigations for such kind of problems in laboratory experiments are extremely hard due to the limitation of current techniques. As an alternative, the numerical method, like the discrete element method (DEM) 1 or bonded particle method (BPM), 2 has been proved to be useful for modeling geomaterials at the grain level. Since the 1980s, there have been several fluid approaches proposed for solving pore fluid flow and its coupling with solid particles in the framework of DEM.Hakuno and Tarumi 3 first combined DEM and Darcy fluid flow (DFF) to analyze liquefaction of saturated sands under seismic excitation. In this method, the excess pore water pressure was taken into account by tracing /journal/nag the change of individual pore volumes formed by neighboring particles and the dissipation of excess pore water pressure was accomplished by two permeability coefficients for water moving through pores. However, only the tendency of gradually increased excess pore water pressure was captured and the fully liquefaction condition was not observed. In order to avoid the complicated individual pore volume calculation, an alternative method was proposed to consider the generation of excess pore water pressure at cell level rather than at pore level. 4 Applications of DEM-DFF in undrained behaviors of saturated sands and upward seepage were performed by Shafipour and Soroush 5 and Goodarzi et al. 6 However, this co...

“…The periodic boundary condition (PBC) is used to reduce the computation scale of a large (or infinite) model or eliminate the boundary effects of simulations [23]. Its application in DEM simulation of triaxial tests can be traced back to Cundall [24].…”

Section: Periodic Boundary Conditionmentioning

confidence: 99%

Discrete element modelling of flexible membrane boundaries for triaxial tests

Computers and Geotechnics

et al. 2019

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The discrete element modelling (DEM) of triaxial tests plays a critical role in 2 unveiling fundamental properties of particulate materials, but the numerical 3 implementation of a flexible membrane boundary for the testing still imposes 4 problems. In this study, a robust algorithm was proposed to reproduce a flexible 5 membrane boundary in triaxial testing. The equivalence of strain energy enables the 6 particle-scale parameters representing the flexible membrane to be directly 7 determined from the real geometric and material parameters of the membrane. Then 8 the proposed flexible membrane boundary was implemented in the context of discrete 9 element simulation of triaxial testing and was validated with laboratory experiments. 10 Furthermore, comparisons of triaxial tests with flexible and rigid boundaries were 11 performed from macro-scale to meso-scale. The results show that the boundary 12 condition has limited influences on the stress-strain behaviour but a relatively large 13 impact on the volumetric change, the failure mode, the distribution of contact forces, 14 and the fabric evolution of particles in the specimen during triaxial testing. 15