共查询到20条相似文献,搜索用时 15 毫秒
1.
An Indirect-Forcing Immersed Boundary Method for Incompressible Viscous Flows with Interfaces on Irregular Domains 下载免费PDF全文
Zhijun Tan K. M. Lim B. C. Khoo & Desheng Wang 《Communications In Computational Physics》2009,6(5):997-1021
An indirect-forcing immersed boundary method for solving the incompressible
Navier-Stokes equations involving the interfaces and irregular domains is developed.
The rigid boundaries and interfaces are represented by a number of Lagrangian
control points. Stationary rigid boundaries are embedded in the Cartesian grid and
singular forces at the rigid boundaries are applied to impose the prescribed velocity
conditions. The singular forces at the interfaces and the rigid boundaries are then distributed
to the nearby Cartesian grid points using the immersed boundary method. In
the present work, the singular forces at the rigid boundaries are computed implicitly
by solving a small system of equations at each time step to ensure that the prescribed
velocity condition at the rigid boundary is satisfied exactly. For deformable interfaces,
the forces that the interface exerts on the fluid are computed from the configuration
of the elastic interface and are applied to the fluid. The Navier-Stokes equations are
discretized using finite difference method on a staggered uniform Cartesian grid by a
second order accurate projection method. The ability of the method to simulate viscous
flows with interfaces on irregular domains is demonstrated by applying to the
rotational flow problem, the relaxation of an elastic membrane and flow in a constriction
with an immersed elastic membrane. 相似文献
2.
Immersed Boundary – Thermal Lattice Boltzmann Methods for Non-Newtonian Flows Over a Heated Cylinder: A Comparative Study 下载免费PDF全文
A. Amiri Delouei M. Nazari M. H. Kayhani & S. Succi 《Communications In Computational Physics》2015,18(2):489-515
In this study, we compare different diffuse and sharp interface schemes of direct-forcing immersed boundary — thermal lattice Boltzmann method (IB-TLBM) for non-Newtonian flow over a heated circular cylinder. Both effects of the discrete lattice and the body force on the momentum and energy equations are considered, by applying the split-forcing Lattice Boltzmann equations. A new technique based on predetermined parameters of direct forcing IB-TLBM is presented for computing the Nusselt number. The study covers both steady and unsteady regimes (20相似文献
3.
An Efficient Immersed Boundary-Lattice Boltzmann Method for the Simulation of Thermal Flow Problems 下载免费PDF全文
Yang Hu Decai Li Shi Shu & Xiaodong Niu 《Communications In Computational Physics》2016,20(5):1210-1257
In this paper, a diffuse-interface immersed boundary method (IBM) is proposed
to treat three different thermal boundary conditions (Dirichlet, Neumann, Robin)
in thermal flow problems. The novel IBM is implemented combining with the lattice
Boltzmann method (LBM). The present algorithm enforces the three types of thermal
boundary conditions at the boundary points. Concretely speaking, the IBM for the
Dirichlet boundary condition is implemented using an iterative method, and its main
feature is to accurately satisfy the given temperature on the boundary. The Neumann
and Robin boundary conditions are implemented in IBM by distributing the jump of
the heat flux on the boundary to surrounding Eulerian points, and the jump is obtained
by applying the jump interface conditions in the normal and tangential directions. A
simple analysis of the computational accuracy of IBM is developed. The analysis indicates
that the Taylor-Green vortices problem which was used in many previous studies
is not an appropriate accuracy test example. The capacity of the present thermal immersed
boundary method is validated using four numerical experiments: (1) Natural
convection in a cavity with a circular cylinder in the center; (2) Flows over a heated
cylinder; (3) Natural convection in a concentric horizontal cylindrical annulus; (4) Sedimentation
of a single isothermal cold particle in a vertical channel. The numerical
results show good agreements with the data in the previous literatures. 相似文献
4.
Numerical Study of Stability and Accuracy of the Immersed Boundary Method Coupled to the Lattice Boltzmann BGK Model 下载免费PDF全文
Yongguang Cheng Luoding Zhu & Chunze Zhang 《Communications In Computational Physics》2014,16(1):136-168
This 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. 相似文献
5.
The Immersed Interface Method for Non-Smooth Rigid Objects in Incompressible Viscous Flows 下载免费PDF全文
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
6.
Immersed Boundary-Lattice Boltzmann Coupling Scheme for Fluid-Structure Interaction with Flexible Boundary 下载免费PDF全文
Yongguang Cheng Hui Zhang & Chang Liu 《Communications In Computational Physics》2011,9(5):1375-1396
Coupling the immersed boundary (IB) method and the lattice Boltzmann
(LB) method might be a promising approach to simulate fluid-structure interaction
(FSI) problems with flexible structures and complex boundaries, because the former
is a general simulation method for FSIs in biological systems, the latter is an efficient
scheme for fluid flow simulations, and both of them work on regular Cartesian grids.
In this paper an IB-LB coupling scheme is proposed and its feasibility is verified. The
scheme is suitable for FSI problems concerning rapid flexible boundary motion and a
large pressure gradient across the boundary. We first analyze the respective concepts,
formulae and advantages of the IB and LB methods, and then explain the coupling
strategy and detailed implementation procedures. To verify the effectiveness and accuracy,
FSI problems arising from the relaxation of a distorted balloon immersed in a
viscous fluid, an unsteady wake flow caused by an impulsively started circular cylinder
at Reynolds number 9500, and an unsteady vortex shedding flow past a suddenly
started rotating circular cylinder at Reynolds number 1000 are simulated. The first
example is a benchmark case for flexible boundary FSI with a large pressure gradient
across the boundary, the second is a fixed complex boundary problem, and the third is
a typical moving boundary example. The results are in good agreement with the analytical
and existing numerical data. It is shown that the proposed scheme is capable of
modeling flexible boundary and complex boundary problems at a second-order spatial
convergence; the volume leakage defect of the conventional IB method has been remedied
by using a new method of introducing the unsteady and non-uniform external
force; and the LB method makes the IB method simulation simpler and more efficient. 相似文献
7.
An Implicit Algorithm for High-Order DG/FV Schemes for Compressible Flows on 2D Arbitrary Grids 下载免费PDF全文
Laiping Zhang Ming Li Wei Liu & Xin He 《Communications In Computational Physics》2015,17(1):287-316
A Newton/LU-SGS (lower-upper symmetric Gauss-Seidel) iteration implicit
method was developed to solve two-dimensional Euler and Navier-Stokes equations
by the DG/FV hybrid schemes on arbitrary grids. The Newton iteration was employed
to solve the nonlinear system, while the linear system was solved with LU-SGS iteration.
The effect of several parameters in the implicit scheme, such as the CFL number,
the Newton sub-iteration steps, and the update frequency of Jacobian matrix, was investigated
to evaluate the performance of convergence history. Several typical test
cases were simulated, and compared with the traditional explicit Runge-Kutta (RK)
scheme. Firstly the Couette flow was tested to validate the order of accuracy of the
present DG/FV hybrid schemes. Then a subsonic inviscid flow over a bump in a channel
was simulated and the effect of parameters was alsoinvestigated. Finally, the implicit
algorithm was applied to simulate a subsonic inviscid flow over a circular cylinder
and the viscous flow in a square cavity. The numerical results demonstrated that
the present implicit scheme can accelerate the convergence history efficiently. Choosing
proper parameters would improve the efficiency of the implicit scheme. Moreover,
in the same framework, the DG/FV hybrid schemes are more efficient than the same
order DG schemes. 相似文献
8.
S. C. Fu R. M. C. So & W. W. F. Leung 《Communications In Computational Physics》2011,9(5):1257-1283
The objective of this paper is to seek an alternative to the numerical simulation
of the Navier-Stokes equations by a method similar to solving the BGK-type
modeled lattice Boltzmann equation. The proposed method is valid for both gas and
liquid flows. A discrete flux scheme (DFS) is used to derive the governing equations
for two distribution functions; one for mass and another for thermal energy. These
equations are derived by considering an infinitesimally small control volume with a
velocity lattice representation for the distribution functions. The zero-order moment
equation of the mass distribution function is used to recover the continuity equation,
while the first-order moment equation recovers the linear momentum equation. The
recovered equations are correct to the first order of the Knudsen number (Kn); thus,
satisfying the continuum assumption. Similarly, the zero-order moment equation of
the thermal energy distribution function is used to recover the thermal energy equation.
For aerodynamic flows, it is shown that the finite difference solution of the DFS
is equivalent to solving the lattice Boltzmann equation (LBE) with a BGK-type model
and a specified equation of state. Thus formulated, the DFS can be used to simulate a
variety of aerodynamic and hydrodynamic flows. Examples of classical aeroacoustics,
compressible flow with shocks, incompressible isothermal and non-isothermal Couette
flows, stratified flow in a cavity, and double diffusive flow inside a rectangle are used
to demonstrate the validity and extent of the DFS. Very good to excellent agreement
with known analytical and/or numerical solutions is obtained; thus lending evidence
to the DFS approach as an alternative to solving the Navier-Stokes equations for fluid
flow simulations. 相似文献
9.
A DDG Method with a Residual-Based Artificial Viscosity for the Transonic/Supersonic Compressible Flow 下载免费PDF全文
Xiaofeng He Kun Wang Yiwei Feng Tiegang Liu & Xiaojun Wang 《Communications In Computational Physics》2022,31(4):1134-1161
In this work, a direct discontinuous Galerkin (DDG) method with artificial
viscosity is developed to solve the compressible Navier-Stokes equations for simulating the transonic or supersonic flow, where the DDG approach is used to discretize
viscous and heat fluxes. A strong residual-based artificial viscosity (AV) technique is
proposed to be applied in the DDG framework to handle shock waves and layer structures appearing in transonic or supersonic flow, which promotes convergence and robustness. Moreover, the AV term is added to classical BR2 methods for comparison.
A number of 2-D and 3-D benchmarks such as airfoils, wings, and a full aircraft are
presented to assess the performance of the DDG framework with the strong residual-based AV term for solving the two dimensional and three dimensional Navier-Stokes
equations. The proposed framework provides an alternative robust and efficient approach for numerically simulating the multi-dimensional compressible Navier-Stokes
equations for transonic or supersonic flow. 相似文献
10.
A Diffuse-Interface Lattice Boltzmann Method for the Dendritic Growth with Thermosolutal Convection 下载免费PDF全文
Chengjie Zhan Zhenhua Chai Baochang Shi Ping Jiang Shaoning Geng & Dongke Sun 《Communications In Computational Physics》2023,33(4):1164-1188
In this work, we proposed a diffuse-interface model for the dendritic growth
with thermosolutal convection. In this model, the sharp boundary between the fluid
and solid dendrite is firstly replaced by a thin but nonzero thickness diffuse interface,
which is described by the order parameter, and the diffuse-interface based governing
equations for the dendritic growth are presented. To solve the model for the dendritic
growth with thermosolutal convection, we also developed a diffuse-interface multi-relaxation-time lattice Boltzmann (LB) method. In this method, the order parameter
in the phase-field equation is combined into the force caused by the fluid-solid interaction, and the treatment on the complex fluid-solid interface can be avoided. In addition, four LB models are designed for the phase-field equation, concentration equation, temperature equation and the Navier-Stokes equations in a unified framework.
Finally, we performed some simulations of the dendritic growth to test the present
diffuse-interface LB method, and found that the numerical results are in good agreements with some previous works. 相似文献
11.
A Hybrid Immersed Boundary-Lattice Boltzmann Method for Simulation of Viscoelastic Fluid Flows Interaction with Complex Boundaries 下载免费PDF全文
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
12.
In this paper we study optimal shape design problems for systems governed by the Navier-Stokes equations. Optimality conditions are presented. A numerical example for the design of an axisymmetric solid body surrounded by a Navier-Stokes flow is given. 相似文献
13.
As arboreal primates move through the jungle, they are immersed in visual motion that they must distinguish from the movement of predators and prey. We recorded dorsal medial superior temporal (MSTd) cortical neuronal responses to visual motion stimuli simulating self-movement and object motion. MSTd neurons encode the heading of simulated self-movement in three-dimensional (3-D) space. 3-D heading responses can be evoked either by the large patterns of visual motion in optic flow or by the visual object motion seen when an observer passes an earth-fixed landmark. Responses to naturalistically combined optic flow and object motion depend on their relative directions: an object moving as part of the optic flow field has little effect on neuronal responses. In contrast, an object moving separately from the optic flow field has large effects, decreasing the amplitude of the population response and shifting the population's heading estimate to match the direction of object motion as the object moves toward central vision. These effects parallel those seen in human heading perception with minimal effects of objects moving with the optic flow and substantial effects of objects violating the optic flow. We conclude that MSTd can contribute to navigation by supporting 3-D heading estimation, potentially switching from optic flow to object cues when a moving object passes in front of the observer. 相似文献
14.
A Parallel Domain Decomposition Algorithm for Simulating Blood Flow with Incompressible Navier-Stokes Equations with Resistive Boundary Condition 下载免费PDF全文
We introduce and study a parallel domain decomposition algorithm for
the simulation of blood flow in compliant arteries using a fully-coupled system of
nonlinear partial differential equations consisting of a linear elasticity equation and
the incompressible Navier-Stokes equations with a resistive outflow boundary condition. The system is discretized with a finite element method on unstructured moving
meshes and solved by a Newton-Krylov algorithm preconditioned with an overlapping restricted additive Schwarz method. The resistive outflow boundary condition
plays an interesting role in the accuracy of the blood flow simulation and we provide a
numerical comparison of its accuracy with the standard pressure type boundary condition. We also discuss the parallel performance of the implicit domain decomposition
method for solving the fully coupled nonlinear system on a supercomputer with a few
hundred processors. 相似文献
15.
A Robust Immersed Boundary-Lattice Boltzmann Method for Simulation of Fluid-Structure Interaction Problems 下载免费PDF全文
Jie Wu Jing Wu Jiapu Zhan Ning Zhao & Tongguang Wang 《Communications In Computational Physics》2016,20(1):156-178
A robust immersed boundary-lattice Boltzmann method (IB-LBM) is proposed
to simulate fluid-structure interaction (FSI) problems in this work. Compared
with the conventional IB-LBM, the current method employs the fractional step technique
to solve the lattice Boltzmann equation (LBE) with a forcing term. Consequently,
the non-physical oscillation of body force calculation, which is frequently encountered
in the traditional IB-LBM, is suppressed greatly. It is of importance for the simulation
of FSI problems. In the meanwhile, the no-slip boundary condition is strictly satisfied
by using the velocity correction scheme. Moreover, based on the relationship between
the velocity correction and forcing term, the boundary force can be calculated accurately
and easily. A few test cases are first performed to validate the current method.
Subsequently, a series of FSI problems, including the vortex-induced vibration of a circular
cylinder, an elastic filament flapping in the wake of a fixed cylinder and sedimentation
of particles, are simulated. Based on the good agreement between the current
results and those in the literature, it is demonstrated that the proposed IB-LBM has the
capability to handle various FSI problems effectively. 相似文献
16.
Sheng Xu 《Communications In Computational Physics》2012,12(2):528-543
An iterative solver based on the immersed interface method is proposed to solve the pressure in a two-fluid flow on a Cartesian grid with second-order accuracy in the infinity norm. The iteration is constructed by introducing an unsteady term in the pressure Poisson equation. In each iteration step, a Helmholtz equation is solved on the Cartesian grid using FFT. The combination of the iteration and the immersed interface method enables the solver to handle various jump conditions across two-fluid interfaces. This solver can also be used to solve Poisson equations on irregular domains. 相似文献
17.
Finite Volume Lattice Boltzmann Method for Nearly Incompressible Flows on Arbitrary Unstructured Meshes 下载免费PDF全文
A genuine finite volume method based on the lattice Boltzmann equation
(LBE) for nearly incompressible flows is developed. The proposed finite volume lattice
Boltzmann method (FV-LBM) is grid-transparent, i.e., it requires no knowledge of
cell topology, thus it can be implemented on arbitrary unstructured meshes for effective
and efficient treatment of complex geometries. Due to the linear advection term in
the LBE, it is easy to construct multi-dimensional schemes. In addition, inviscid and
viscous fluxes are computed in one step in the LBE, as opposed to in two separate steps
for the traditional finite-volume discretization of the Navier-Stokes equations. Because
of its conservation constraints, the collision term of the kinetic equation can be treated
implicitly without linearization or any other approximation, thus the computational
efficiency is enhanced. The collision with multiple-relaxation-time (MRT) model is
used in the LBE. The developed FV-LBM is of second-order convergence. The proposed
FV-LBM is validated with three test cases in two-dimensions: (a) the Poiseuille
flow driven by a constant body force; (b) the Blasius boundary layer; and (c) the steady
flow past a cylinder at the Reynolds numbers Re=10, 20, and 40. The results verify the
designed accuracy and efficacy of the proposed FV-LBM. 相似文献
18.
A Jacobian-Free Newton Krylov Implicit-Explicit Time Integration Method for Incompressible Flow Problems 下载免费PDF全文
We have introduced a fully second order IMplicit/EXplicit (IMEX) time integration technique for solving the compressible Euler equations plus nonlinear heat conduction problems (also known as the radiation hydrodynamics problems) in Kadioglu et al., J. Comp. Physics [22,24]. In this paper, we study the implications when this method is applied to the incompressible Navier-Stokes (N-S) equations. The IMEX method is applied to the incompressible flow equations in the following manner. The hyperbolic terms of the flow equations are solved explicitly exploiting the well understood explicit schemes. On the other hand, an implicit strategy is employed for the non-hyperbolic terms. The explicit part is embedded in the implicit step in such a way that it is solved as part of the non-linear function evaluation within the framework of the Jacobian-Free Newton Krylov (JFNK) method [8,29,31]. This is done to obtain a self-consistent implementation of the IMEX method that eliminates the potential order reduction in time accuracy due to the specific operator separation. We employ a simple yet quite effective fractional step projection methodology (similar to those in [11,19,21,30]) as our preconditioner inside the JFNK solver. We present results from several test calculations. For each test, we show second order time convergence. Finally, we present a study for the algorithm performance of the JFNK solver with the new projection method based preconditioner. 相似文献
19.
In this paper, a novel implementation of immersed interface method combined
with Stokes solver on a MAC staggered grid for solving the steady two-fluid
Stokes equations with interfaces. The velocity components along the interface are introduced
as two augmented variables and the resulting augmented equation is then
solved by the GMRES method. The augmented variables and/or the forces are related
to the jumps in pressure and the jumps in the derivatives of both pressure and velocity,
and are interpolated using cubic splines and are then applied to the fluid through
the jump conditions. The Stokes equations are discretized on a staggered Cartesian
grid via a second order finite difference method and solved by the conjugate gradient
Uzawa-type method. The numerical results show that the overall scheme is second order
accuracy. The major advantages of the present IIM-Stokes solver are the efficiency
and flexibility in terms of types of fluid flow and different boundary conditions. The
proposed method avoids solution of the pressure Poisson equation, and comparisons
are made to show the advantages of time savings by the present method. The generalized
two-phase Stokes solver with correction terms has also been applied to incompressible
two-phase Navier-Stokes flow. 相似文献
20.
Are extensions to continuum formulations for solving fluid dynamic problems in the transition-to-rarefied regimes viable alternatives to particle methods? It
is well known that for increasingly rarefied flow fields, the predictions from continuum
formulation, such as the Navier-Stokes equations lose accuracy. These inaccuracies are
attributed primarily to the linear approximations of the stress and heat flux terms in the
Navier-Stokes equations. The inclusion of higher-order terms, such as Burnett or high-order moment equations, could improve the predictive capabilities of such continuum
formulations, but there has been limited success in the shock structure calculations, especially for the high Mach number case. Here, after reformulating the viscosity and heat
conduction coefficients appropriate for the rarefied flow regime, we will show that the
Navier-Stokes-type continuum formulation may still be properly used. The equations
with generalization of the dissipative coefficients based on the closed solution of the
Bhatnagar-Gross-Krook (BGK) model of the Boltzmann equation, are solved using the
gas-kinetic numerical scheme. This paper concentrates on the non-equilibrium shock
structure calculations for both monatomic and diatomic gases. The Landau-Teller-Jeans
relaxation model for the rotational energy is used to evaluate the quantitative difference
between the translational and rotational temperatures inside the shock layer. Variations
of shear stress, heat flux, temperatures, and densities in the internal structure of the
shock waves are compared with, (a) existing theoretical solutions of the Boltzmann solution, (b) existing numerical predictions of the direct simulation Monte Carlo (DSMC)
method, and (c) available experimental measurements. The present continuum formulation for calculating the shock structures for monatomic and diatomic gases in the
Mach number range of 1.2 to 12.9 is found to be satisfactory. 相似文献