scholarly journals NUMERICAL STUDY OF THE MICROSTRUCTURE OF A DILUTE SUSPENSION TO ASSESS ITS THIXOTROPIC BEHAVIOR BY A TWO-WAY COUPLING SCHEME

2020 ◽  
Author(s):  
TOMOHIRO FUKUI ◽  
MISA KAWAGUCHI ◽  
KOJI MORINISHI
Keyword(s):  
Numerical Study ◽  
Coupling Scheme ◽  
Thixotropic Behavior ◽  
Dilute Suspension

Numerical Study of Stability and Accuracy of the Immersed Boundary Method Coupled to the Lattice Boltzmann BGK Model

2014 ◽  
Vol 16 (1) ◽  
pp. 136-168 ◽  
Author(s):  
Yongguang Cheng ◽  
Luoding Zhu ◽  
Chunze Zhang
Keyword(s):  
Lattice Boltzmann ◽  
Numerical Study ◽  
Rigid Wall ◽  
Segment Length ◽  
Immersed Boundary ◽  
Coupling Scheme ◽  
Circular Membrane ◽  
Shearing Flow ◽  
Dirac Delta ◽  
Forcing Term

AbstractThis paper aims to study the numerical features of a coupling scheme between the immersed boundary (IB) method and the lattice Boltzmann BGK (LBGK) model by four typical test problems: the relaxation of a circular membrane, the shearing flow induced by a moving fiber in the middle of a channel, the shearing flow near a non-slip rigid wall, and the circular Couette flow between two inversely rotating cylinders. The accuracy and robustness of the IB-LBGK coupling scheme, the performances of different discrete Dirac delta functions, the effect of iteration on the coupling scheme, the importance of the external forcing term treatment, the sensitivity of the coupling scheme to flow and boundary parameters, the velocity slip near non-slip rigid wall, and the origination of numerical instabilities are investigated in detail via the four test cases. It is found that the iteration in the coupling cycle can effectively improve stability, the introduction of a second-order forcing term in LBGK model is crucial, the discrete fiber segment length and the orientation of the fiber boundary obviously affect accuracy and stability, and the emergence of both temporal and spatial fluctuations of boundary parameters seems to be the indication of numerical instability. These elaborate results shed light on the nature of the coupling scheme and may benefit those who wish to use or improve the method.

Simulation of a Full-Scale CO2 Fracture Propagation Test

2018 ◽  
Author(s):  
Gaute Gruben ◽  
Stephane Dumoulin ◽  
Håkon Nordhagen ◽  
Morten Hammer ◽  
Svend T. Munkejord
Keyword(s):  
Fluid Dynamics ◽  
Numerical Model ◽  
Numerical Study ◽  
Crack Opening ◽  
Fracture Propagation ◽  
Full Scale ◽  
Coupling Scheme ◽  
Outer Diameter ◽  
Fe Model ◽  
Set Up

In this study, we present results from a numerical model of a full-scale fracture propagation test where the pipe sections are filled with impure, dense liquid-phase carbon dioxide. All the pipe sections had a 24″ outer diameter and a diameter/thickness ratio of ∼32. A near symmetric telescopic set-up with increasing toughness in the West and East directions was applied. Due to the near symmetric conditions in both set-up and results, only the East direction is modelled in the numerical study. The numerical model is built in the framework of the commercial finite element (FE) software LS-DYNA. The fluid dynamics is solved using an in-house computational fluid dynamics (CFD) solver which is coupled with the FE solver through a user-defined loading subroutine. As part of the coupling scheme, the FE model sends the crack opening profile to the CFD solver which returns the pressure from the fluid. The pipeline is discretized by shell elements, while the backfill is represented by the smoothed-particle hydrodynamics (SPH) method. The steel pipe is described by the J2 constitutive model and an energy-based fracture criterion, while the Mohr-Coulomb material model is applied for the backfill material. The CFD solver applies a one-dimensional homogeneous equilibrium model where the thermodynamic properties of the CO2 are represented by the Peng-Robinson equation-of-state (EOS). The results from the simulations in terms of crack velocity and pressure agree well with the experimental data for the low and medium toughness pipe sections, while a conservative prediction is given for the high-toughness section. Further work for strengthening the reliability of the model to predict the arrest vs. no-arrest boundary of a running ductile fracture is addressed.

CASRock—a code to simulate THMC processes in fractured geological media

2021 ◽  
Author(s):  
Pengzhi Pan
Keyword(s):  
Numerical Study ◽  
Fractured Rock ◽  
Failure Process ◽  
Coupling Scheme ◽  
State Variables ◽  
Heterogeneous Rock ◽  
Rock Failure Process ◽  
Coupled Thm Processes ◽  
High Level ◽  
Cracking Process

<p>This work presents the advancement of a self-developed Cellular Automata Software for engineering Rockmass fracturing processes (CASRock, http://en.casrock.cn/) in the applications of thermo-hydro-mechanical-chemical (THMC) processes in fractured geological media. It contains a series of previous developed numerical systems, namely EPCA for simulation of heterogeneous rock failure process, VEPCA for visco elastoplastic analysis, D-EPCA for rock dynamic response simulation, THMC-EPCA for coupled THMC processes in geological media and RDCA for simulation of rock cracking process from continuity to discontinuity. In CASRock, the non-isothermal, unsaturated fluid flow, mechanical process and chemical reaction are sequentially coupled by updating all the state variables using cellular automaton technique and finite difference method on spatial and temporal scale, respectively. The Lagrangian method is used to simulate the particle transport. The control equations, coupling scheme and numerical implementation are briefly introduced. Several applications, including  in the background of high level nuclear waste disposal are provided to show the abilities of CASRock in the simulation of coupling processes between physical fields. These applications include, (1) stability analysis of engineering rockmass under mechanical loading, (2) numerical study on coupled TM processes in hard rock pillar, (3) study on coupled THM processes in engineering barrier, (4) simulation of the THMC process in fractured rock.</p>

scholarly journals Possible Routes to Obtain Enhanced Magnetoresistance in a Driven Quantum Heterostructure with a Quasi-Periodic Spacer

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1021
Author(s):  
Arpita Koley ◽  
Santanu K. Maiti ◽  
Laura M. Pérez ◽  
Judith Helena Ojeda Silva ◽  
David Laroze
Keyword(s):  
Layered Structure ◽  
Numerical Study ◽  
Tight Binding ◽  
Light Irradiation ◽  
Effect Of Temperature ◽  
Coupling Scheme ◽  
Magnetic Layers ◽  
Periodic Potentials ◽  
Ferromagnetic Layers ◽  
Multilayered Systems

In this work, we perform a numerical study of magnetoresistance in a one-dimensional quantum heterostructure, where the change in electrical resistance is measured between parallel and antiparallel configurations of magnetic layers. This layered structure also incorporates a non-magnetic spacer, subjected to quasi-periodic potentials, which is centrally clamped between two ferromagnetic layers. The efficiency of the magnetoresistance is further tuned by injecting unpolarized light on top of the two sided magnetic layers. Modulating the characteristic properties of different layers, the value of magnetoresistance can be enhanced significantly. The site energies of the spacer is modified through the well-known Aubry–André and Harper (AAH) potential, and the hopping parameter of magnetic layers is renormalized due to light irradiation. We describe the Hamiltonian of the layered structure within a tight-binding (TB) framework and investigate the transport properties through this nanojunction following Green’s function formalism. The Floquet–Bloch (FB) anstaz within the minimal coupling scheme is introduced to incorporate the effect of light irradiation in TB Hamiltonian. Several interesting features of magnetotransport properties are represented considering the interplay between cosine modulated site energies of the central region and the hopping integral of the magnetic regions that are subjected to light irradiation. Finally, the effect of temperature on magnetoresistance is also investigated to make the model more realistic and suitable for device designing. Our analysis is purely a numerical one, and it leads to some fundamental prescriptions of obtaining enhanced magnetoresistance in multilayered systems.

Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Lennard Jones
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