共查询到20条相似文献,搜索用时 15 毫秒
1.
A Hybrid Immersed Boundary-Lattice Boltzmann Method for Simulation of Viscoelastic Fluid Flows Interaction with Complex Boundaries
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M. H. Sedaghat A. A. H. Bagheri M. M. Shahmardan M. Norouzi B. C. Khoo & P. G. Jayathilake 《Communications In Computational Physics》2021,29(5):1411-1445
In this study, a numerical technique based on the Lattice Boltzmann method
is presented to model viscoelastic fluid interaction with complex boundaries which are
commonly seen in biological systems and industrial practices. In order to accomplish
numerical simulation of viscoelastic fluid flows, the Newtonian part of the momentum
equations is solved by the Lattice Boltzmann Method (LBM) and the divergence of the
elastic tensor, which is solved by the finite difference method, is added as a force term
to the governing equations. The fluid-structure interaction forces are implemented
through the Immersed Boundary Method (IBM). The numerical approach is validated
for Newtonian and viscoelastic fluid flows in a straight channel, a four-roll mill geometry as well as flow over a stationary and rotating circular cylinder. Then, a numerical
simulation of Oldroyd-B fluid flow around a confined elliptical cylinder with different
aspect ratios is carried out for the first time. Finally, the present numerical approach
is used to simulate a biological problem which is the mucociliary transport process of
human respiratory system. The present numerical results are compared with appropriate analytical, numerical and experimental results obtained from the literature. 相似文献
2.
The Immersed Interface Method for Non-Smooth Rigid Objects in Incompressible Viscous Flows
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Yang Liu & Sheng Xu 《Communications In Computational Physics》2021,29(2):510-533
In the immersed interface method, an object in a flow is formulated as a singular force, and jump conditions caused by the singular force are incorporated into numerical schemes to compute the flow. Previous development of the method considered
only smooth objects. We here extend the method to handle non-smooth rigid objects
with sharp corners in 2D incompressible viscous flows. We represent the boundary of
an object as a polygonal curve moving through a fixed Cartesian grid. We compute
necessary jump conditions to achieve boundary condition capturing on the object. We
incorporate the jump conditions into finite difference schemes to solve the flow on the
Cartesian grid. The accuracy, efficiency and robustness of our method are tested using
canonical flow problems. The results demonstrate that the method has second-order
accuracy for the velocity and first-order accuracy for the pressure in the infinity norm,
and is extremely efficient and robust to simulate flows around non-smooth complex
objects. 相似文献
3.
Arnab Ghosh Alessandro Gabbana Herman Wijshoff & Federico Toschi 《Communications In Computational Physics》2023,33(1):349-366
The immersed boundary method has emerged as an efficient approach for
the simulation of finite-sized solid particles in complex fluid flows. However, one of
the well known shortcomings of the method is the limited support for the simulation
of light particles, i.e. particles with a density lower than that of the surrounding fluid,
both in terms of accuracy and numerical stability.Although a broad literature exists, with several authors reporting different approaches
for improving the stability of the method, most of these attempts introduce extra complexities and are very costly from a computational point of view.In this work, we introduce an effective force stabilizing technique, allowing to extend
the stability range of the method by filtering spurious oscillations arising when dealing
with light-particles, pushing down the particle-to-fluid density ratio as low as 0.04.
We thoroughly validate the method comparing with both experimental and numerical
data available in literature. 相似文献
4.
Lattice Boltzmann Simulations of Two Linear Microswimmers Using the Immersed Boundary Method
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D. Geyer S. Ziegler A. Sukhov M. Hubert A.-S. Smith O. Aouane P. Malgaretti & J. Harting 《Communications In Computational Physics》2023,33(1):310-329
The performance of a single or the collection of microswimmers strongly
depends on the hydrodynamic coupling among their constituents and themselves. We
present a numerical study for a single and a pair of microswimmers based on lattice
Boltzmann method (LBM) simulations. Our numerical algorithm consists of two separable parts. Lagrange polynomials provide a discretization of the microswimmers and
the lattice Boltzmann method captures the dynamics of the surrounding fluid. The
two components couple via an immersed boundary method. We present data for a
single swimmer system and our data also show the onset of collective effects and, in
particular, an overall velocity increment of clusters of swimmers. 相似文献
5.
Kinetic Slip Boundary Condition for Isothermal Rarefied Gas Flows Through Static Non-Planar Geometries Based on the Regularized Lattice-Boltzmann Method
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Jean-Michel Tucny David Vidal Sé bastien Leclaire & Franç ois Bertrand 《Communications In Computational Physics》2022,31(3):816-868
The simulation of rarefied gas flows through complex porous media is challenging due to the tortuous flow pathways inherent to such structures. The Lattice
Boltzmann method (LBM) has been identified as a promising avenue to solve flows
through complex geometries due to the simplicity of its scheme and its high parallel
computational efficiency. It has been proposed to model the stress-strain relationship
with the extended Navier-Stokes equations rather than attempting to directly solve
the Boltzmann equation. However, a regularization technique is required to filter out
non-resolved higher-order components with a low-order velocity scheme. Although
slip boundary conditions (BCs) have been proposed for the non-regularized multiple
relaxation time LBM (MRT-LBM) for planar geometries, previous slip BCs have never
been verified extensively with the regularization technique. In this work, following
an extensive literature review on the imposition of slip BCs for rarefied flows with the
LBM, it is proven that earlier values for kinetic parameters developed to impose slip
BCs are inaccurate for the regularized MRT-LBM and differ between the D2Q9 and
D3Q15 schemes. The error was eliminated for planar flows and good agreement between analytical solutions for arrays of cylinders and spheres was found with a wide
range of Knudsen numbers. 相似文献
6.
This paper presents a fourth-order Cartesian grid based boundary integral
method (BIM) for heterogeneous interface problems in two and three dimensional
space, where the problem interfaces are irregular and can be explicitly given by parametric curves or implicitly defined by level set functions. The method reformulates the
governing equation with interface conditions into boundary integral equations (BIEs)
and reinterprets the involved integrals as solutions to some simple interface problems
in an extended regular region. Solution of the simple equivalent interface problems for
integral evaluation relies on a fourth-order finite difference method with an FFT-based
fast elliptic solver. The structure of the coefficient matrix is preserved even with the
existence of the interface. In the whole calculation process, analytical expressions of
Green’s functions are never determined, formulated or computed. This is the novelty
of the proposed kernel-free boundary integral (KFBI) method. Numerical experiments
in both two and three dimensions are shown to demonstrate the algorithm efficiency
and solution accuracy even for problems with a large diffusion coefficient ratio. 相似文献
7.
Friedemann Klass Alessandro Gabbana & Andreas Bartel 《Communications In Computational Physics》2023,33(1):101-117
We present the development of a non-reflecting boundary condition, based
on the Local One-Dimensional Inviscid (LODI) approach, for Lattice Boltzmann Models working with multi-speed stencils.We test and evaluate the LODI implementation with numerical benchmarks, showing significant accuracy gains with respect to the results produced by a simple zero-gradient condition. We also implement a simplified approach, which allows handling
the unknown distribution functions spanning several layers of nodes in a unified way,
still preserving a comparable level of accuracy with respect to the standard formulation. 相似文献
8.
A Simple 3D Immersed Interface Method for Stokes Flow with Singular Forces on Staggered Grids
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Weiyi Wang & Zhijun Tan 《Communications In Computational Physics》2021,30(1):227-254
In this paper, a fairly simple 3D immersed interface method based on the
CG-Uzawa type method and the level set representation of the interface is employed
for solving three-dimensional Stokes flow with singular forces along the interface. The
method is to apply the Taylor's expansions only along the normal direction and incorporate the jump conditions up to the second normal derivatives into the finite difference schemes. A second order geometric iteration algorithm is employed for computing orthogonal projections on the surface with third-order accuracy. The Stokes
equations are discretized involving the correction terms on staggered grids and then
solved by the conjugate gradient Uzawa type method. The major advantages of the
present method are the special simplicity, the ability in handling the Dirichlet boundary conditions, and no need of the pressure boundary condition. The method can
also preserve the volume conservation and the discrete divergence free condition very
well. The numerical results show that the proposed method is second order accurate
and efficient. 相似文献
9.
A projection-based reduced order model (ROM) based on the Fourier collocation method is proposed for compressible flows. The incorporation of localized
artificial viscosity model and filtering is pursued to enhance the robustness and accuracy of the ROM for shock-dominated flows. Furthermore, for Euler systems, ROMs
built on the conservative and the skew-symmetric forms of the governing equation are
compared. To ensure efficiency, the discrete empirical interpolation method (DEIM)
is employed. An alternative reduction approach, exploring the sparsity of viscosity
is also investigated for the viscous terms. A number of one- and two-dimensional
benchmark cases are considered to test the performance of the proposed models. Results show that stable computations for shock-dominated cases can be achieved with
ROMs built on both the conservative and the skew-symmetric forms without additional stabilization components other than the viscosity model and filtering. Under
the same parameters, the skew-symmetric form shows better robustness and accuracy
than its conservative counterpart, while the conservative form is superior in terms of
efficiency. 相似文献
10.
Multi-Scale Deep Neural Network (MscaleDNN) Methods for Oscillatory Stokes Flows in Complex Domains
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In this paper, we study a multi-scale deep neural network (MscaleDNN)
as a meshless numerical method for computing oscillatory Stokes flows in complex
domains. The MscaleDNN employs a multi-scale structure in the design of its DNN
using radial scalings to convert the approximation of high frequency components of
the highly oscillatory Stokes solution to one of lower frequencies. The MscaleDNN
solution to the Stokes problem is obtained by minimizing a loss function in terms of $L^2$ norm of the residual of the Stokes equation. Three forms of loss functions are investigated based on vorticity-velocity-pressure, velocity-stress-pressure, and velocity-gradient of velocity-pressure formulations of the Stokes equation. We first conduct a
systematic study of the MscaleDNN methods with various loss functions on the Kovasznay flow in comparison with normal fully connected DNNs. Then, Stokes flows
with highly oscillatory solutions in a 2-D domain with six randomly placed holes are
simulated by the MscaleDNN. The results show that MscaleDNN has faster convergence and consistent error decays in the simulation of Kovasznay flow for all three
tested loss functions. More importantly, the MscaleDNN is capable of learning highly
oscillatory solutions when the normal DNNs fail to converge. 相似文献
11.
Burnett Order Stress and Spatially-Dependent Boundary Conditions for the Lattice Boltzmann Method
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Timothy Reis 《Communications In Computational Physics》2020,27(1):167-186
Stress boundary conditions for the lattice Boltzmann equation that are consistent to Burnett order are proposed and imposed using a moment-based method.
The accuracy of the method with complicated spatially-dependent boundary conditions for stress and velocity is investigated using the regularized lid-driven cavity flow.
The complete set of boundary conditions, which involve gradients evaluated at the
boundaries, are implemented locally. A recently-derived collision operator with modified equilibria and velocity-dependent collision rates to reduce the defect in Galilean
invariance is also investigated. Numerical results are in excellent agreement with existing benchmark data and exhibit second-order convergence. The lattice Boltzmann
stress field is studied and shown to depart significantly from the Newtonian viscous
stress when the ratio of Mach to Reynolds numbers is not negligibly small. 相似文献
12.
Adaptive Fully Implicit Simulator with Multilevel Schwarz Methods for Gas Reservoir Flows in Fractured Porous Media
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Large-scale reservoir modeling and simulation of gas reservoir flows in fractured porous media is currently an important topic of interest in petroleum engineering. In this paper, the dual-porosity dual-permeability (DPDP) model coupled with
the Peng-Robinson equation of state (PR-EoS) is used for the mathematical model of
the gas reservoir flow in fractured porous media. We develop and study a parallel and
highly scalable reservoir simulator based on an adaptive fully implicit scheme and
an inexact Newton type method to solve this dual-continuum mathematical model.
In the approach, an explicit-first-step, single-diagonal-coefficient, diagonally implicit
Runge–Kutta (ESDIRK) method with adaptive time stepping is proposed for the fully
implicit discretization, which is second-order and L-stable. And then we focus on the
family of Newton–Krylov methods for the solution of a large sparse nonlinear system
of equations arising at each time step. To accelerate the convergence and improve the
scalability of the solver, a class of multilevel monolithic additive Schwarz methods is
employed for preconditioning. Numerical results on a set of ideal as well as realistic
flow problems are used to demonstrate the efficiency and the robustness of the proposed methods. Experiments on a supercomputer with several thousand processors
are also carried out to show that the proposed reservoir simulator is highly scalable. 相似文献
13.
A Simulation Approach Including Underresolved Scales for Two-Component Fluid Flows in Multiscale Porous Structures
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Hiroshi Otomo Rafael Salazar-Tio Jingjing Yang Hongli Fan rew Fager Bernd Crouse Raoyang Zhang & Hudong Chen 《Communications In Computational Physics》2023,33(1):189-213
In this study, we develop computational models and a methodology for
accurate multicomponent flow simulation in underresolved multiscale porous structures [1]. It is generally impractical to fully resolve the flow in porous structures
with large length-scale differences due to the tremendously high computational expense. The flow contributions from underresolved scales should be taken into account
with proper physics modeling and simulation processes. Using precomputed physical properties such as the absolute permeability, $K_0,$ the capillary pressure-saturation
curve, and the relative permeability, $K_r,$ in typical resolved porous structures, the local fluid force is determined and applied to simulations in the underresolved regions,
which are represented by porous media. In this way, accurate flow simulations in
multiscale porous structures become feasible.To evaluate the accuracy and robustness of this method, a set of benchmark test cases
are simulated for both single-component and two-component flows in artificially constructed multiscale porous structures. Using comparisons with analytic solutions and
results with much finer resolution resolving the porous structures, the simulated results are examined. Indeed, in all cases, the results successfully show high accuracy
with proper input of $K_0,$ capillary pressure, and $K_r.$ Specifically, imbibition patterns,
entry pressure, residual component patterns, and absolute/relative permeability are
accurately captured with this approach. 相似文献
14.
An Efficient Neural-Network and Finite-Difference Hybrid Method for Elliptic Interface Problems with Applications
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Wei-Fan Hu Te-Sheng Lin Yu-Hau Tseng & Ming-Chih Lai 《Communications In Computational Physics》2023,33(4):1090-1105
A new and efficient neural-network and finite-difference hybrid method is
developed for solving Poisson equation in a regular domain with jump discontinuities
on embedded irregular interfaces. Since the solution has low regularity across the interface, when applying finite difference discretization to this problem, an additional
treatment accounting for the jump discontinuities must be employed. Here, we aim to
elevate such an extra effort to ease our implementation by machine learning methodology. The key idea is to decompose the solution into singular and regular parts. The
neural network learning machinery incorporating the given jump conditions finds the
singular solution, while the standard five-point Laplacian discretization is used to obtain the regular solution with associated boundary conditions. Regardless of the interface geometry, these two tasks only require supervised learning for function approximation and a fast direct solver for Poisson equation, making the hybrid method easy
to implement and efficient. The two- and three-dimensional numerical results show
that the present hybrid method preserves second-order accuracy for the solution and
its derivatives, and it is comparable with the traditional immersed interface method in
the literature. As an application, we solve the Stokes equations with singular forces to
demonstrate the robustness of the present method. 相似文献
15.
Comparison of Lattice Boltzmann,Finite Element and Volume of Fluid Multicomponent Methods for Microfluidic Flow Problems and the Jetting of Microdroplets
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Karun P. N. Datadien Gianluca Di Staso Christian Diddens Herman M. A. Wijshoff & Federico Toschi 《Communications In Computational Physics》2023,33(3):912-936
We show that the lattice Boltzmann method (LBM) based color-gradient
model with a central moments formulation (CG-CM) is capable of accurately simulating the droplet-on-demand inkjetting process on a micrometer length scale by comparing it to the Arbitrary Lagrangian Eulerian Finite Element Method (ALE-FEM). A
full jetting cycle is simulated using both CG-CM and ALE-FEM and results are quantitatively compared by measuring the ejected ink velocity, volume and contraction rate.
We also show that the individual relevant physical phenomena are accurately captured
by considering three test-cases; droplet oscillation, ligament contraction and capillary
rise. The first two cases test accuracy for a dynamic system where surface tension is
the driving force and the third case is designed to test wetting boundary conditions.
For the first two cases we also compare the CG-CM and ALE-FEM results to Volume
of Fluid (VOF) simulations. Comparison of the three methods shows close agreement
when compared to each other and analytical solutions, where available. Finally wedemonstrate that asymmetric jetting is achievable using 3D CG-CM simulations utilizing asymmetric wetting conditions inside the jet-nozzle. This allows for systematic
investigation into the physics of asymmetric jetting, e.g. due to jet-nozzle manufacturing imperfections or due to other disturbances. 相似文献
16.
J. A. Barasona J. Vicente I. Díez‐Delgado J. Aznar C. Gortzar M. J. Torres 《Transboundary and Emerging Diseases》2017,64(4):1148-1158
The members of the Mycobacterium tuberculosis complex (MTC) cause tuberculosis (TB). Infection is transmitted within and between livestock and wildlife populations, thus hampering TB control. Indirect transmission might be facilitated if MTC bacteria persist in the environment long enough to represent a risk of exposure to different species sharing the same habitat. We have, for the first time, addressed the relationship between environmental MTC persistence and the use of water resources in two TB endemic areas in southern Spain with the objective of identifying the presence of environmental MTC and its driving factors at ungulates’ water aggregation points. Camera‐trap monitoring and MTC diagnosis (using a new MTC complex‐specific PCR technique) were carried out at watering sites. Overall, 55.8% of the water points tested positive for MTC in mud samples on the shore, while 8.9% of them were positive in the case of water samples. A higher percentage of MTC‐positive samples was found at those waterholes where cachectic animals were identified using camera‐trap monitoring, and at the smallest waterholes. Our results help to understand the role of indirect routes of cross‐species TB transmission and highlight the importance of certain environmental features in maintaining infection in multihost systems. This will help to better target actions and implement control strategies for TB at the wildlife/livestock interface. 相似文献
17.
Tiezheng Qian Xiao-Ping Wang & Ping Sheng 《Communications In Computational Physics》2006,1(1):1-52
The no-slip boundary condition, i.e., zero fluid velocity relative to the solid at the
fluid-solid interface, has been very successful in describing many macroscopic flows. A problem
of principle arises when the no-slip boundary condition is used to model the hydrodynamics
of immiscible-fluid displacement in the vicinity of the moving contact line, where the interface
separating two immiscible fluids intersects the solid wall. Decades ago it was already known
that the moving contact line is incompatible with the no-slip boundary condition, since the
latter would imply infinite dissipation due to a non-integrable singularity in the stress near
the contact line. In this paper we first present an introductory review of the problem. We
then present a detailed review of our recent results on the contact-line motion in immiscible
two-phase flow, from molecular dynamics (MD) simulations to continuum hydrodynamics
calculations. Through extensive MD studies and detailed analysis, we have uncovered the
slip boundary condition governing the moving contact line, denoted the generalized Navier
boundary condition. We have used this discovery to formulate a continuum hydrodynamic
model whose predictions are in remarkable quantitative agreement with the MD simulation
results down to the molecular scale. These results serve to affirm the validity of the generalized
Navier boundary condition, as well as to open up the possibility of continuum hydrodynamic
calculations of immiscible flows that are physically meaningful at the molecular level. 相似文献
18.
A Fourth-Order Upwinding Embedded Boundary Method (UEBM) for Maxwell's Equations in Media with Material Interfaces: Part I
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In this paper, we present a new fourth-order upwinding embedded boundary method (UEBM) over Cartesian grids, originally proposed in the Journal of Computational Physics [190 (2003), pp. 159-183.] as a second-order method for treating material interfaces for Maxwell's equations. In addition to the idea of the UEBM to evolve solutions at interfaces, we utilize the ghost fluid method to construct finite difference approximation of spatial derivatives at Cartesian grid points near the material interfaces. As a result, Runge-Kutta type time discretization can be used for the semidiscretized system to yield an overall fourth-order method, in contrast to the original second-order UEBM based on a Lax-Wendroff type difference. The final scheme allows time step sizes independent of the interface locations. Numerical examples are given to demonstrate the fourth-order accuracy as well as the stability of the method. We tested the scheme for several wave problems with various material interface locations, including electromagnetic scattering of a plane wave incident on a planar boundary and a two-dimensional electromagnetic application with an interface parallel to the y-axis. 相似文献
19.
A Highly Scalable Boundary Integral Equation and Walk-on-Spheres (BIE-WOS) Method for the Laplace Equation with Dirichlet Data
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In this paper, we study a highly scalable communication-free parallel domain boundary decomposition algorithm for the Laplace equation based on a hybrid method combining boundary integral equations and walk-on-spheres (BIE-WOS)
method, which provides a numerical approximation of the Dirichlet-to-Neumann
(DtN) mapping for the Laplace equation. The BIE-WOS is a local method on the
boundary of the domain and does not require a structured mesh, and only needs a
covering of the domain boundary by patches and a local mesh for each patch for a local BIE. A new version of the BIE-WOS method with second kind integral equations is
introduced for better error controls. The effect of errors from the Feynman-Kac formula
based path integral WOS method on the overall accuracy of the BIE-WOS method is
analyzed for the BIEs, especially in the calculation of the right hand sides of the BIEs.
For the special case of flat patches, it is shown that the second kind integral equation
of BIE-WOS method can be simplified where the local BIE solutions can be given in
closed forms. A key advantage of the parallel BIE-WOS method is the absence of communications during the computation of the DtN mapping on individual patches of
the boundary, resulting in a complete independent computation using a large number
of cluster nodes. In addition, the BIE-WOS has an intrinsic capability of fault tolerance for exascale computations. The nearly linear scalability of the parallel BIE-WOS
method on a large-scale cluster with 6400 CPU cores is verified for computing the DtN
mapping of exterior Laplace problems with Dirichlet data for several domains. 相似文献
20.
Weak Galerkin and Continuous Galerkin Coupled Finite Element Methods for the Stokes-Darcy Interface Problem
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Hui Peng Qilong Zhai Ran Zhang & Shangyou Zhang 《Communications In Computational Physics》2020,28(3):1147-1175
We consider a model of coupled free and porous media flow governed by
Stokes equation and Darcy's law with the Beavers-Joseph-Saffman interface condition.
In this paper, we propose a new numerical approach for the Stokes-Darcy system. The
approach employs the classical finite element method for the Darcy region and the
weak Galerkin finite element method for the Stokes region. We construct corresponding discrete scheme and prove its well-posedness. The estimates for the corresponding numerical approximation are derived. Finally, we present some numerical experiments to validate the efficiency of the approach for solving this problem. 相似文献