scholarly journals Mesoscale dynamic coupling of finite- and discrete-element methods for fluid–particle interactions

2014 ◽  
Vol 372 (2021) ◽  
pp. 20130386 ◽  
Author(s):  
S. Srivastava ◽  
K. Yazdchi ◽  
S. Luding
Keyword(s):  
Stokes Equations ◽  
Particle Density ◽  
Coarse Graining ◽  
Particle Method ◽  
Discrete Element ◽  
Fluid Particle ◽  
Momentum Exchange ◽  
Wide Range ◽  
Flow Through ◽  
Element Method

A new method for two-way fluid–particle coupling on an unstructured mesoscopically coarse mesh is presented. In this approach, we combine a (higher order) finite-element method (FEM) on the moving mesh for the fluid with a soft sphere discrete-element method for the particles. The novel feature of the proposed scheme is that the FEM mesh is a dynamic Delaunay triangulation based on the positions of the moving particles. Thus, the mesh can be multi-purpose: it provides (i) a framework for the discretization of the Navier–Stokes equations, (ii) a simple tool for detecting contacts between moving particles, (iii) a basis for coarse-graining or upscaling, and (iv) coupling with other physical fields (temperature, electromagnetic, etc.). This approach is suitable for a wide range of dilute and dense particulate flows, because the mesh resolution adapts with particle density in a given region. Two-way momentum exchange is implemented using semi-empirical drag laws akin to other popular approaches; for example, the discrete particle method, where a finite-volume solver on a coarser, fixed grid is used. We validate the methodology with several basic test cases, including single- and double-particle settling with analytical and empirical expectations, and flow through ordered and random porous media, when compared against finely resolved FEM simulations of flow through fixed arrays of particles.

scholarly journals Modelling the variation in the behaviour of pre-fractured rocks subjected to hydraulic fracturing with permeability of the rock matrix using finite-discrete element method

2020 ◽  
Vol 205 ◽  
pp. 08001
Author(s):  
Shahrzad Roshankhah ◽  
Arman K. Nejad ◽  
Orlando Teran ◽  
Kami Mohammadi
Keyword(s):  
Rock Mass ◽  
Finite Elements ◽  
Hydraulic Fracturing ◽  
Discrete Element Method ◽  
Fractured Rocks ◽  
Discrete Element ◽  
Fracture Network ◽  
Rock Matrix ◽  
Flow Through ◽  
Element Method

In this study, we present the results of two-dimensional numerical simulations for the effects of rock matrix permeability on the behaviour of hydraulic fractures in intact and pre-fractured rocks. The simulations are performed using the Finite-Discrete Element Method (FDEM). In this method, the deformation and fluid pressure fields within the porous rock blocks, pre-existing fracture network, and hydraulically induced fractures are calculated through a fully coupled hydromechanical scheme. Furthermore, new fractures can initiate in crack elements located between each pair of finite elements and can propagate in any path that the boundary and loading conditions require according to non-linear fracture mechanics criteria. Fluid channels are also defined between pairs of finite elements simulating the inter-connected flow paths through porous media. Four models of the rock mass are created in this study: (i) homogeneous-impermeable, (ii) homogeneous-permeable, (iii) heterogeneous-impermeable matrix, and (iv) heterogeneous-permeable matrix. Heterogeneous rock masses contain a discrete fracture network (natural fractures) in the rock mass structure. Hydraulic fracturing is modelled in domains of 40×40 m2 with the four different structures and mass transport capacities, and the results are compared to each other. The results highlight the significant effect of diffusive fluid flow through rock blocks, in addition to the flow through fracture network, on the global hydromechanical behaviour of the rock mass. These results help to understand the governing hydromechanical processes taking place in fractured rocks with matrix of different permeability, such as granites, shales, carbonate rocks, and sandstones and the extent of complexities required to model their behaviour to achieve reasonable accuracy.

Simulation of Fluid Flow Through a Granular Bed

2006 ◽  
Author(s):  
Arezou Jafari ◽  
S. Mohammad Mousavi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Packed Bed ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Wide Range ◽  
Duct Geometry ◽  
Flow Through

Numerical study of flow through random packing of non-overlapping spheres in a cylindrical geometry is investigated. Dimensionless pressure drop has been studied for a fluid through the porous media at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), and numerical solution of Navier-Stokes equations in three dimensional porous packed bed illustrated in excellent agreement with those reported by Macdonald [1979] in the range of Reynolds number studied. The results compare to the previous work (Soleymani et al., 2002) show more accurate conclusion because the problem of channeling in a duct geometry. By injection of solute into the system, the dispersivity over a wide range of flow rate has been investigated. It is shown that the lateral fluid dispersion coefficients can be calculated by comparing the concentration profiles of solute obtained by numerical simulations and those derived analytically by solving the macroscopic dispersion equation for the present geometry.

scholarly journals Coupling Simulation Algorithm of Discrete Element Method and Finite Element Method for Particle Damper

2009 ◽  
Vol 28 (3) ◽  
pp. 197-204 ◽  
Author(s):  
Zhaowang Xia ◽  
Xiandong Liu ◽  
Yingchun Shan ◽  
Xinghu Li
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Discrete Element Method ◽  
Particle Density ◽  
Discrete Element ◽  
Experimental Results ◽  
Theoretical Research ◽  
Simulation Algorithm ◽  
Cantilever Plate ◽  
Element Method

One advantage of the particle damper is that its property is independent of the surrounding temperature. This allows it to be used in harsh environments where traditional dampers fail. But current design of this damper mainly depends on experimental results because of a lack of theoretical research. In this paper, an investigation into particle dampers is performed analytically and experimentally. A coupling simulation algorithm based on the discrete element method and finite element method is presented. Comparison between the analytical and experimental results shows that simulation of the response of a cantilever plate with a particle damper is accurate. It is shown that the response of the cantilever plate depends on the mass-fill ratio and particle density of the particle damper.

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 Resolved CFD-DEM simulation of blood flow with a reduced-order RBC model

2021 ◽  
Author(s):  
Achuth Nair Balachandran Nair ◽  
Stefan Pirker ◽  
Mahdi Saeedipour
Keyword(s):  
Blood Flow ◽  
Discrete Element Method ◽  
Discrete Element ◽  
Computational Method ◽  
Dem Simulation ◽  
Reduced Order ◽  
Wide Range ◽  
Channel Constriction ◽  
Good Agreement ◽  
Element Method

AbstractMathematical modeling of the blood flow with a resolved description of biological cells mechanics such as red blood cell (RBC) has been a challenge in the past decades as it involves physical complexities and demands high computational costs. In the present study, we propose an approach for efficient simulation of blood flow with several suspended RBCs. In this approach, we employ our previously proposed reduced-order model for deformable particles (Nair et al. in Comput Part Mech 7:593–601, 2020) to mimic the mechanical behavior of an individual RBC as a cluster of overlapping spheres interconnected by flexible mathematical bonds. This discrete element method-based model is then coupled with a fluid flow solver using the immersed boundary method with continuous forcing in the context of computational fluid dynamics-discrete element method (CFD-DEM) coupling. The present computational method is tested with a couple of validation cases in which the single RBC dynamics, as well as the blood flow with several RBCs, were tested in comparison with existing literature date. First, the RBC deformation index in shear flow at different shear rates is studied with a good accuracy. Then, the blood flow in micro-tubes of different diameters and hematocrits was simulated. The key characteristics of blood flow such as cell-free layer (CFL) thickness, Fahraeus effect and the relative apparent viscosity are used as the validation metrics. The proposed approach can predict the formation of the migration of RBC toward the tube center-line and the CFL thickness in good agreement with previous measurement and simulations. Furthermore, the model is employed to study the CFL enhancement for plasma separation based on channel constriction. The simulation results compute the CFL thickness downstream of the channel constriction in good agreement with the experiments in a wide range of flow rates and constriction lengths. The original contribution of this study lies in proposing an efficient resolved CFD-DEM simulation method for blood flows with many RBCs which can be employed for numerical investigation of bio-microfluidic applications.

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