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Duo Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Three-dimensional Lattice-Boltzmann Model for liquid water transport and oxygen diffusion in cathode of polymer electrolyte membrane fuel cell with electrochemical reaction
    Electrochimica Acta, 2018
    Co-Authors: Duo Zhang, Qiong Cai, Sai Gu
    Abstract:

    Polymer electrolyte membrane(PEM) fuel cells have higher efficiency and energy density and are capable of rapidly adjusting to power demands. Effective water management is one of the key issues for increasing the efficiency of PEMFC. In the current study, a three-dimensional(3D) Lattice Boltzmann Model is developed to simulate the water transport and oxygen diffusion in the gas diffusion layer(GDL) of PEM fuel cells with electrochemical reaction on the catalyst layer taken into account. In this paper, we demonstrate that this Model is able to predict the liquid and gas flow fields within the 3D GDL structure and how they change with time. With the two-phase flow and electrochemical reaction coupled in the Model, concentration of oxygen through the GDL and current density distribution can also be predicted. The Model is then used to investigate the effect of microporous layer on the cell performance in 2D to reduce the computational cost. The results clearly show that the liquid water content can be reduced with the existence of microporous layer and thus the current density can be increased.

  • application of a high density ratio Lattice Boltzmann Model for the droplet impingement on flat and spherical surfaces
    International Journal of Thermal Sciences, 2014
    Co-Authors: Duo Zhang, Konstantinos Papadikis
    Abstract:

    In the current study, a 3-dimensional Lattice Boltzmann Model which can tolerate high density ratios is employed to simulate the impingement of a liquid droplet onto a flat and a spherical target. The four phases of droplet impact on a flat surface, namely, the kinematic, spreading, relaxation and equilibrium phase, have been obtained for a range of Weber and Reynolds numbers. The predicted maximum spread factor is in good agreement with experimental data published in the literature. For the impact of the liquid droplet onto a spherical target, the temporal variation of the film thickness on the target surface is investigated. The three different temporal phases of the film dynamics, namely, the initial drop deformation phase, the inertia dominated phase and the viscosity dominated phase are reproduced and studied. The effect of the droplet Reynolds number and the target-to-drop size ratio on the film flow dynamics is investigated.

  • three dimensional multi relaxation time Lattice Boltzmann Model for the drop impact on a dry surface at large density ratio
    International Journal of Multiphase Flow, 2014
    Co-Authors: Duo Zhang, Konstantinos Papadikis
    Abstract:

    Extensive application of the multiphase Lattice Boltzmann Model to realistic fluid flows is often restricted by the numerical instabilities induced at high liquid-to-gas density ratios, and at low viscosities. In this paper, a three-dimensional multi-relaxation time (MRT) Lattice Boltzmann Model with an improved forcing scheme is reported for simulating multiphase flows at high liquid-to-gas density ratios and relatively high Reynolds numbers. The Model is based on a recently presented Model in the literature. Firstly, the MRT multiphase Model is evaluated by verifying Laplace’s law and achieving thermodynamic consistency for a static droplet. Then, a relationship between the fluid–solid interaction potential parameter and contact angle is investigated. Finally, the improved three-dimensional MRT Lattice Boltzmann Model is employed in the simulation of the impingement of a liquid droplet onto a flat surface for a range of Weber and Reynolds numbers. The dynamics of the droplet spreading is reproduced and the predicted maximum spread factor is in good agreement with experimental data published in the literature.

Baochang Shi - One of the best experts on this subject based on the ideXlab platform.

  • a block triple relaxation time Lattice Boltzmann Model for nonlinear anisotropic convection diffusion equations
    Computers & Mathematics With Applications, 2020
    Co-Authors: Yong Zhao, Zhenhua Chai, Baochang Shi
    Abstract:

    Abstract A block triple-relaxation-time (B-TriRT) Lattice Boltzmann Model for general nonlinear anisotropic convection–diffusion equations (NACDEs) is proposed, and the Chapman–Enskog analysis shows that the present B-TriRT Model can recover the NACDEs correctly. There are some striking features of the present B-TriRT Model: firstly, the relaxation matrix of B-TriRT Model is partitioned into three relaxation parameter blocks, rather than a diagonal matrix in general multiple-relaxation-time (MRT) Model; secondly, based on the analysis of half-way bounce-back (HBB) scheme for Dirichlet boundary conditions, we obtain an expression to determine the relaxation parameters; thirdly, the anisotropic diffusion tensor can be recovered by the relaxation parameter block that corresponds to the first-order moment of non-equilibrium distribution function. A number of simulations of isotropic and anisotropic convection–diffusion equations are conducted to validate the present B-TriRT Model. The results indicate that the present Model has a second-order accuracy in space, and is also more accurate and more stable than some available Lattice Boltzmann Models.

  • a multiple relaxation time Lattice Boltzmann Model for general nonlinear anisotropic convection diffusion equations
    Journal of Scientific Computing, 2016
    Co-Authors: Zhenhua Chai, Baochang Shi, Zhaoli Guo
    Abstract:

    In this paper, based on the previous work (Shi and Guo in Phys Rev E 79:016701, 2009), we develop a multiple-relaxation-time (MRT) Lattice Boltzmann Model for general nonlinear anisotropic convection---diffusion equation (NACDE), and show that the NACDE can be recovered correctly from the present Model through the Chapman---Enskog analysis. We then test the MRT Model through some classic CDEs, and find that the numerical results are in good agreement with analytical solutions or some available results. Besides, the numerical results also show that similar to the single-relaxation-time Lattice Boltzmann Model or so-called BGK Model, the present MRT Model also has a second-order convergence rate in space. Finally, we also perform a comparative study on the accuracy and stability of the MRT Model and BGK Model by using two examples. In terms of the accuracy, both the analysis and numerical results show that a numerical slip on the boundary would be caused in the BGK Model, and cannot be eliminated unless the relaxation parameter is fixed to be a special value, while the numerical slip in the MRT Model can be overcome once the relaxation parameters satisfy some constrains. The results in terms of stability also demonstrate that the MRT Model could be more stable than the BGK Model through tuning the free relaxation parameters.

  • multiple relaxation time Lattice Boltzmann Model for generalized newtonian fluid flows
    Journal of Non-newtonian Fluid Mechanics, 2011
    Co-Authors: Zhenhua Chai, Baochang Shi, Zhaoli Guo, Fumei Rong
    Abstract:

    The generalized Newtonian fluid, as an important kind of non-Newtonian fluids, has been widely used in both science and engineering. In this paper, we present a multiple-relaxation-time Lattice Boltzmann Model for generalized Newtonian fluid, and validate the Model through a detailed comparison with analytical solutions and some published results. The accuracy and stability of the present Model are also studied, and compared with those of the popular single-relaxation-time Lattice Boltzmann Model. Finally, the limit and potential of the multiple-relaxation-time Lattice Boltzmann Model are briefly discussed.

  • Lattice Boltzmann Model for nonlinear convection diffusion equations
    Physical Review E, 2009
    Co-Authors: Baochang Shi, Zhaoli Guo
    Abstract:

    A Lattice Boltzmann Model for convection-diffusion equation with nonlinear convection and isotropic-diffusion terms is proposed through selecting equilibrium distribution function properly. The Model can be applied to the common real and complex-valued nonlinear evolutionary equations, such as the nonlinear Schrodinger equation, complex Ginzburg-Landau equation, Burgers-Fisher equation, nonlinear heat conduction equation, and sine-Gordon equation, by using a real and complex-valued distribution function and relaxation time. Detailed simulations of these equations are performed, and it is found that the numerical results agree well with the analytical solutions and the numerical solutions reported in previous studies.

  • A novel Lattice Boltzmann Model for the Poisson equation
    Applied Mathematical Modelling, 2008
    Co-Authors: Zhenhua Chai, Baochang Shi
    Abstract:

    In this paper, a novel Lattice Boltzmann Model is proposed to solve the Poisson equation through modifying equilibrium distribution function. Compared with previous Models, which can be viewed as the solvers to diffusion equation, the present Model is a genuine solver to the Poisson equation, and the transient term derived by previous Models is eliminated. Numerical solutions agree well with analytical solutions, which indicates the potential of the present Model for solving the Poisson equation.

Zhenhua Chai - One of the best experts on this subject based on the ideXlab platform.

  • a block triple relaxation time Lattice Boltzmann Model for nonlinear anisotropic convection diffusion equations
    Computers & Mathematics With Applications, 2020
    Co-Authors: Yong Zhao, Zhenhua Chai, Baochang Shi
    Abstract:

    Abstract A block triple-relaxation-time (B-TriRT) Lattice Boltzmann Model for general nonlinear anisotropic convection–diffusion equations (NACDEs) is proposed, and the Chapman–Enskog analysis shows that the present B-TriRT Model can recover the NACDEs correctly. There are some striking features of the present B-TriRT Model: firstly, the relaxation matrix of B-TriRT Model is partitioned into three relaxation parameter blocks, rather than a diagonal matrix in general multiple-relaxation-time (MRT) Model; secondly, based on the analysis of half-way bounce-back (HBB) scheme for Dirichlet boundary conditions, we obtain an expression to determine the relaxation parameters; thirdly, the anisotropic diffusion tensor can be recovered by the relaxation parameter block that corresponds to the first-order moment of non-equilibrium distribution function. A number of simulations of isotropic and anisotropic convection–diffusion equations are conducted to validate the present B-TriRT Model. The results indicate that the present Model has a second-order accuracy in space, and is also more accurate and more stable than some available Lattice Boltzmann Models.

  • a multiple relaxation time Lattice Boltzmann Model for general nonlinear anisotropic convection diffusion equations
    Journal of Scientific Computing, 2016
    Co-Authors: Zhenhua Chai, Baochang Shi, Zhaoli Guo
    Abstract:

    In this paper, based on the previous work (Shi and Guo in Phys Rev E 79:016701, 2009), we develop a multiple-relaxation-time (MRT) Lattice Boltzmann Model for general nonlinear anisotropic convection---diffusion equation (NACDE), and show that the NACDE can be recovered correctly from the present Model through the Chapman---Enskog analysis. We then test the MRT Model through some classic CDEs, and find that the numerical results are in good agreement with analytical solutions or some available results. Besides, the numerical results also show that similar to the single-relaxation-time Lattice Boltzmann Model or so-called BGK Model, the present MRT Model also has a second-order convergence rate in space. Finally, we also perform a comparative study on the accuracy and stability of the MRT Model and BGK Model by using two examples. In terms of the accuracy, both the analysis and numerical results show that a numerical slip on the boundary would be caused in the BGK Model, and cannot be eliminated unless the relaxation parameter is fixed to be a special value, while the numerical slip in the MRT Model can be overcome once the relaxation parameters satisfy some constrains. The results in terms of stability also demonstrate that the MRT Model could be more stable than the BGK Model through tuning the free relaxation parameters.

  • Regularized Lattice Boltzmann Model for a class of convection-diffusion equations
    Physical Review E, 2015
    Co-Authors: Lei Wang, Zhenhua Chai
    Abstract:

    : In this paper, a regularized Lattice Boltzmann Model for a class of nonlinear convection-diffusion equations with variable coefficients is proposed. The main idea of the present Model is to introduce a set of precollision distribution functions that are defined only in terms of macroscopic moments. The Chapman-Enskog analysis shows that the nonlinear convection-diffusion equations can be recovered correctly. Numerical tests, including Fokker-Planck equations, Buckley-Leverett equation with discontinuous initial function, nonlinear convection-diffusion equation with anisotropic diffusion, are carried out to validate the present Model, and the results show that the present Model is more accurate than some available Lattice Boltzmann Models. It is also demonstrated that the present Model is more stable than the traditional single-relaxation-time Model for the nonlinear convection-diffusion equations.

  • multiple relaxation time Lattice Boltzmann Model for generalized newtonian fluid flows
    Journal of Non-newtonian Fluid Mechanics, 2011
    Co-Authors: Zhenhua Chai, Baochang Shi, Zhaoli Guo, Fumei Rong
    Abstract:

    The generalized Newtonian fluid, as an important kind of non-Newtonian fluids, has been widely used in both science and engineering. In this paper, we present a multiple-relaxation-time Lattice Boltzmann Model for generalized Newtonian fluid, and validate the Model through a detailed comparison with analytical solutions and some published results. The accuracy and stability of the present Model are also studied, and compared with those of the popular single-relaxation-time Lattice Boltzmann Model. Finally, the limit and potential of the multiple-relaxation-time Lattice Boltzmann Model are briefly discussed.

  • A novel Lattice Boltzmann Model for the Poisson equation
    Applied Mathematical Modelling, 2008
    Co-Authors: Zhenhua Chai, Baochang Shi
    Abstract:

    In this paper, a novel Lattice Boltzmann Model is proposed to solve the Poisson equation through modifying equilibrium distribution function. Compared with previous Models, which can be viewed as the solvers to diffusion equation, the present Model is a genuine solver to the Poisson equation, and the transient term derived by previous Models is eliminated. Numerical solutions agree well with analytical solutions, which indicates the potential of the present Model for solving the Poisson equation.

Rongzong Huang - One of the best experts on this subject based on the ideXlab platform.

  • phase interface effects in the total enthalpy based Lattice Boltzmann Model for solid liquid phase change
    Journal of Computational Physics, 2015
    Co-Authors: Rongzong Huang
    Abstract:

    Abstract In this paper, phase interface effects, including the differences in thermophysical properties between solid and liquid phases and the numerical diffusion across phase interface, are investigated for the recently developed total enthalpy-based Lattice Boltzmann Model for solid–liquid phase change, which has high computational efficiency by avoiding iteration procedure and linear equation system solving. For the differences in thermophysical properties (thermal conductivity and specific heat) between solid and liquid phases, a novel reference specific heat is introduced to improve the total enthalpy-based Lattice Boltzmann Model, which makes the thermal conductivity and specific heat decoupled. Therefore, the differences in thermal conductivity and specific heat can be handled by the dimensionless relaxation time and equilibrium distribution function, respectively. As for the numerical diffusion across phase interface, it is revealed for the first time and found to be induced by solid–liquid phase change. To reduce such numerical diffusion, multiple-relaxation-time collision scheme is exploited, and a special value (one fourth) for the so-called “magic” parameter, a combination of two relaxation parameters, is found. Numerical tests show that the differences in thermophysical properties can be correctly handled and the numerical diffusion across phase interface can be dramatically reduced. Finally, theoretical analyses are carried out to offer insights into the roles of the reference specific heat and “magic” parameter in the treatments of phase interface effects.

  • a modified multiple relaxation time Lattice Boltzmann Model for convection diffusion equation
    Journal of Computational Physics, 2014
    Co-Authors: Rongzong Huang
    Abstract:

    A modified Lattice Boltzmann Model with multiple relaxation times (MRT) for the convection-diffusion equation (CDE) is proposed. By modifying the relaxation matrix, as well as choosing the corresponding equilibrium distribution function properly, the present Model can recover the CDE with anisotropic diffusion coefficient with no deviation term even when the velocity vector varies generally with space or time through the Chapman-Enskog analysis. This Model is firstly validated by simulating the diffusion of a Gaussian hill, which demonstrates it can handle the anisotropic diffusion problem correctly. Then it is adopted to calculate the longitudinal dispersion coefficient of the Taylor-Aris dispersion. Numerical results show that the present Model can further reduce the numerical error under the condition of non-zero velocity vector, especially when the dimensionless relaxation time is relatively large.

Zhaoli Guo - One of the best experts on this subject based on the ideXlab platform.

  • a multiple relaxation time Lattice Boltzmann Model for general nonlinear anisotropic convection diffusion equations
    Journal of Scientific Computing, 2016
    Co-Authors: Zhenhua Chai, Baochang Shi, Zhaoli Guo
    Abstract:

    In this paper, based on the previous work (Shi and Guo in Phys Rev E 79:016701, 2009), we develop a multiple-relaxation-time (MRT) Lattice Boltzmann Model for general nonlinear anisotropic convection---diffusion equation (NACDE), and show that the NACDE can be recovered correctly from the present Model through the Chapman---Enskog analysis. We then test the MRT Model through some classic CDEs, and find that the numerical results are in good agreement with analytical solutions or some available results. Besides, the numerical results also show that similar to the single-relaxation-time Lattice Boltzmann Model or so-called BGK Model, the present MRT Model also has a second-order convergence rate in space. Finally, we also perform a comparative study on the accuracy and stability of the MRT Model and BGK Model by using two examples. In terms of the accuracy, both the analysis and numerical results show that a numerical slip on the boundary would be caused in the BGK Model, and cannot be eliminated unless the relaxation parameter is fixed to be a special value, while the numerical slip in the MRT Model can be overcome once the relaxation parameters satisfy some constrains. The results in terms of stability also demonstrate that the MRT Model could be more stable than the BGK Model through tuning the free relaxation parameters.

  • multiple relaxation time Lattice Boltzmann Model for generalized newtonian fluid flows
    Journal of Non-newtonian Fluid Mechanics, 2011
    Co-Authors: Zhenhua Chai, Baochang Shi, Zhaoli Guo, Fumei Rong
    Abstract:

    The generalized Newtonian fluid, as an important kind of non-Newtonian fluids, has been widely used in both science and engineering. In this paper, we present a multiple-relaxation-time Lattice Boltzmann Model for generalized Newtonian fluid, and validate the Model through a detailed comparison with analytical solutions and some published results. The accuracy and stability of the present Model are also studied, and compared with those of the popular single-relaxation-time Lattice Boltzmann Model. Finally, the limit and potential of the multiple-relaxation-time Lattice Boltzmann Model are briefly discussed.

  • Lattice Boltzmann Model for nonlinear convection diffusion equations
    Physical Review E, 2009
    Co-Authors: Baochang Shi, Zhaoli Guo
    Abstract:

    A Lattice Boltzmann Model for convection-diffusion equation with nonlinear convection and isotropic-diffusion terms is proposed through selecting equilibrium distribution function properly. The Model can be applied to the common real and complex-valued nonlinear evolutionary equations, such as the nonlinear Schrodinger equation, complex Ginzburg-Landau equation, Burgers-Fisher equation, nonlinear heat conduction equation, and sine-Gordon equation, by using a real and complex-valued distribution function and relaxation time. Detailed simulations of these equations are performed, and it is found that the numerical results agree well with the analytical solutions and the numerical solutions reported in previous studies.

  • Lattice Boltzmann Model for incompressible flows through porous media
    Physical Review E, 2002
    Co-Authors: Zhaoli Guo, Tianshou Zhao
    Abstract:

    In this paper a Lattice Boltzmann Model is proposed for isothermal incompressible flow in porous media. The key point is to include the porosity into the equilibrium distribution, and add a force term to the evolution equation to account for the linear and nonlinear drag forces of the medium (the Darcy's term and the Forcheimer's term). Through the Chapman-Enskog procedure, the generalized Navier-Stokes equations for incompressible flow in porous media are derived from the present Lattice Boltzmann Model. The generalized two-dimensional Poiseuille flow, Couette flow, and lid-driven cavity flow are simulated using the present Model. It is found the numerical results agree well with the analytical and/or the finite-difference solutions.