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Wenan Yong - One of the best experts on this subject based on the ideXlab platform.

  • relaxation rate formula for the entropic lattice boltzmann Method
    arXiv: Computational Physics, 2019
    Co-Authors: Weifeng Zhao, Wenan Yong
    Abstract:

    An elegant and uniform relaxation-rate formula is presented for the entropic lattice Boltzmann Method (ELBM). The formula not only guarantees the discrete time H-theorem at numerical level but also gives full consideration to the consistency with hydrodynamics. With this novel formula, the computational cost of the ELBM is significantly reduced and the Method now can be efficiently used for a broad range of hydrodynamics applications including high Renolds number flows. Moreover, we demonstrate that the grid points where flow fields change drastically are effectively marked by the formula.

  • single node second order boundary schemes for the lattice boltzmann Method
    Journal of Computational Physics, 2017
    Co-Authors: Weifeng Zhao, Wenan Yong
    Abstract:

    Abstract Based on our recently developed Maxwell iteration for the lattice Boltzmann Method, we propose a class of single-node boundary schemes for Dirichlet boundary conditions of the Navier–Stokes equations. The schemes all have second-order accuracy for both straight and curved boundaries. The accuracy and stability of two specific schemes are examined through several numerical experiments. The results validate the second-order accuracy and show that a boundary scheme with a convex combination of distribution functions has better stability.

  • boundary conditions of the lattice boltzmann Method for convection diffusion equations
    Journal of Computational Physics, 2015
    Co-Authors: Juntao Huang, Wenan Yong
    Abstract:

    In this paper, we employ an asymptotic analysis technique and construct two boundary schemes accompanying the lattice Boltzmann Method for convection-diffusion equations with general Robin boundary conditions. One scheme is for straight boundaries, with the boundary points locating at any distance from the lattice nodes, and has second-order accuracy. The other is for curved boundaries, has only first-order accuracy and is much simpler than the existing schemes. Unlike those in the literature, our schemes involve only the current lattice node. Such a "single-node" boundary schemes are highly desirable for problems with complex geometries. The two schemes are validated numerically with a number of examples. The numerical results show the utility of the constructed schemes and very well support our theoretical predications.

Jianhua Qin - One of the best experts on this subject based on the ideXlab platform.

  • an immersed interface lattice boltzmann Method for fluid structure interaction
    Journal of Computational Physics, 2021
    Co-Authors: Jianhua Qin, Ebrahim M Kolahdouz, Boyce E Griffith
    Abstract:

    Abstract An immersed interface-lattice Boltzmann Method (II-LBM) is developed for modeling fluid-structure systems. The key element of this approach is the determination of the jump conditions that are satisfied by the distribution functions within the framework of the lattice Boltzmann Method where forces are imposed along a surface immersed in an incompressible fluid. In this initial II-LBM, the discontinuity related to the normal portion of the interfacial force is sharply resolved by imposing the relevant jump conditions using an approach that is analogous to imposing the corresponding pressure discontinuity in the incompressible Navier-Stokes equations. We show that the jump conditions for the distribution functions are the same in both single-relaxation-time and multi-relaxation-time LBM formulations. Tangential forces are treated using the immersed boundary-lattice Boltzmann Method (IB-LBM). In our implementation, a level set approach is used to impose jump conditions for rigid-body models. For flexible boundary models, we describe the moving interface by interpolating the positions of marker points that move with the fluid. The II-LBM is compared to a direct forcing IB-LBM for rigid-body fluid-structure interaction, and a classical IB-LBM for cases involving elastic interfaces. Higher order accuracy is observed with the II-LBM as compared to the IB-LBM for selected benchmark problems. Because the jump conditions of the distribution function also satisfy the continuity of the velocity field across the interface, the error in the velocity field is much smaller for the II-LBM than the IB-LBM. The II-LBM is also demonstrated to provide superior volume conservation when simulating flexible boundaries.

Yan Peng - One of the best experts on this subject based on the ideXlab platform.

  • application of multi block approach in the immersed boundary lattice boltzmann Method for viscous fluid flows
    Journal of Computational Physics, 2006
    Co-Authors: Yan Peng, Y. T. Chew, Xiyun Lu
    Abstract:

    The immersed boundary-lattice Boltzmann Method was presented recently to simulate the rigid particle motion. It combines the desirable features of the lattice Boltzmann and immersed boundary Methods. It uses a regular Eulerian grid for the flow domain and a Lagrangian grid for the boundary. For the lattice Boltzmann Method, as compared with the single-relaxation-time collision scheme, the multi-relaxation-time collision scheme has better computational stability due to separation of the relaxations of various kinetic models, especially near the geometric singularity. So the multi-relaxation-time collision scheme is used to replace the single-relaxation-time collision scheme in the original immersed boundary-lattice Boltzmann Method. In order to obtain an accurate result, very fine lattice grid is needed near the solid boundary. To reduce the computational effort, local grid refinement is adopted to offer high resolution near a solid body and to place the outer boundary far away from the body. So the multi-block scheme with the multi-relaxation-time collision model is used in the immersed boundary-lattice Boltzmann Method. In each block, uniform lattice spacing can still be used. In order to validate the multi-block approach for the immersed boundary-lattice Boltzmann Method with multi-relaxation-time collision scheme, the numerical simulations of steady and unsteady flows past a circular cylinder and airfoil are carried out and good results are obtained.

  • A momentum exchange-based immersed boundary-lattice Boltzmann Method for simulating incompressible viscous flows
    Physics Letters A, 2006
    Co-Authors: Y. T. Chew, Yan Peng
    Abstract:

    A momentum exchange-based immersed boundary-lattice Boltzmann Method is presented in this Letter for simulating incompressible viscous flows. This Method combines the good features of the lattice Boltzmann Method (LBM) and the immersed boundary Method (IBM) by using two unrelated computational meshes, an Eulerian mesh for the flow domain and a Lagrangian mesh for the solid boundaries in the flow. In this Method, the non-slip boundary condition is enforced by introducing a forcing term into the lattice Boltzmann equation (LBE). Unlike the conventional IBM using the penalty Method with a user-defined parameter or the direct forcing scheme based on the Navier-Stokes (NS) equations, the forcing term is simply calculated by the momentum exchange of the boundary particle density distribution functions, which are interpolated by the Lagrangian polynomials from the underlying Eulerian mesh. Numerical examples show that the present Method can provide very accurate numerical results.

  • SIMULATION OF NATURAL CONVECTION IN A SQUARE CAVITY BY TAYLOR SERIES EXPANSION- AND LEAST SQUARES-BASED LATTICE BOLTZMANN Method
    International Journal of Modern Physics C, 2002
    Co-Authors: Yan Peng, Y. T. Chew
    Abstract:

    The Taylor series expansion- and least squares-based lattice Boltzmann Method (TLLBM) was used in this paper to extend the current thermal model to an arbitrary geometry so that it can be used to solve practical thermo-hydrodynamics in the incompressible limit. The new explicit Method is based on the standard lattice Boltzmann Method (LBM), Taylor series expansion and the least squares approach. The final formulation is an algebraic form and essentially has no limitation on the mesh structure and lattice model. Numerical simulations of natural convection in a square cavity on both uniform and nonuniform grids have been carried out. Favorable results were obtained and compared well with the benchmark data. It was found that, to get the same order of accuracy, the number of mesh points used on the nonuniform grid is much less than that used on the uniform grid.

Xiyun Lu - One of the best experts on this subject based on the ideXlab platform.

  • application of multi block approach in the immersed boundary lattice boltzmann Method for viscous fluid flows
    Journal of Computational Physics, 2006
    Co-Authors: Yan Peng, Y. T. Chew, Xiyun Lu
    Abstract:

    The immersed boundary-lattice Boltzmann Method was presented recently to simulate the rigid particle motion. It combines the desirable features of the lattice Boltzmann and immersed boundary Methods. It uses a regular Eulerian grid for the flow domain and a Lagrangian grid for the boundary. For the lattice Boltzmann Method, as compared with the single-relaxation-time collision scheme, the multi-relaxation-time collision scheme has better computational stability due to separation of the relaxations of various kinetic models, especially near the geometric singularity. So the multi-relaxation-time collision scheme is used to replace the single-relaxation-time collision scheme in the original immersed boundary-lattice Boltzmann Method. In order to obtain an accurate result, very fine lattice grid is needed near the solid boundary. To reduce the computational effort, local grid refinement is adopted to offer high resolution near a solid body and to place the outer boundary far away from the body. So the multi-block scheme with the multi-relaxation-time collision model is used in the immersed boundary-lattice Boltzmann Method. In each block, uniform lattice spacing can still be used. In order to validate the multi-block approach for the immersed boundary-lattice Boltzmann Method with multi-relaxation-time collision scheme, the numerical simulations of steady and unsteady flows past a circular cylinder and airfoil are carried out and good results are obtained.

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

  • contact angle measurement in lattice boltzmann Method
    Computers & Mathematics With Applications, 2018
    Co-Authors: Bingfang Huang, Chunlei Wang, Chaoying Zhang
    Abstract:

    Abstract Contact angle is an essential characteristic in wetting, capillarity and moving contact line; however, although contact angle phenomena are effectively simulated, an accurate and real-time measurement for contact angle has not been well studied in computational fluid dynamics, especially in dynamic environments. Here, we design a geometry-based mesoscopic scheme for on-the-spot measurement of the contact angle in the lattice Boltzmann Method. The measuring results without gravity effect are in good agreement with the benchmarks from the spherical cap Method. The performances of the scheme are further verified in gravitational environments by simulating sessile and pendent droplets on smooth solid surfaces and dynamic contact angle hysteresis on chemically heterogeneous surfaces. This scheme is simple and computationally efficient. It requires only the local data and is independent of multiphase models.

  • contact angle measurement in lattice boltzmann Method
    arXiv: Computational Physics, 2017
    Co-Authors: Bingfang Huang, Chunlei Wang, Chaoying Zhang
    Abstract:

    Contact angle is an essential characteristic in wetting, capillarity and moving contact line; however, although contact angle phenomena are effectively simulated, an accurate and real-time measurement for contact angle has not been well studied in computational fluid dynamics, especially in dynamic environments. Here, we design a geometry-based mesoscopic scheme to onthesport measure the contact angle in the lattice Boltzmann Method. The computational results without gravity effect are in excellent agreement with the benchmarks from the spherical cap Method. The qualities of the scheme are further verified in gravitational environments by simulating sessile and pendent droplets on smooth solid surfaces and contact angle hysteresis on chemically heterogeneous surfaces. This scheme is simple, efficient and requires only the local data. It is independent of multiphase models and can be easily extended to 3D dynamic contact angle measurements.