Results 1  10
of
34
Lattice Boltzmann method for moving boundaries
, 2003
"... We propose a lattice Boltzmann method to treat moving boundary problems for solid objects moving in a fluid. The method is based on the simple bounceback boundary scheme and interpolations. The proposed method is tested in two flows past an impulsively started cylinder moving in a channel in two di ..."
Abstract

Cited by 36 (1 self)
 Add to MetaCart
We propose a lattice Boltzmann method to treat moving boundary problems for solid objects moving in a fluid. The method is based on the simple bounceback boundary scheme and interpolations. The proposed method is tested in two flows past an impulsively started cylinder moving in a channel in two dimensions: (a) the flow past an impulsively started cylinder moving in a transient Couette flow; and (b) the flow past an impulsively started cylinder moving in a channel flow at rest. We obtain satisfactory results and also verify the Galilean invariance of the lattice Boltzmann method.
Simulation of fluid particle separation in realistic threee dimensional fiber structures
, 2003
"... Methods from stochastic geometry allow to construct models which are very good representations of the real complexity of Nonwovens. These realistic models are used as boundaries for a fluid dynamic simulation with a parallel Lattice Boltzmann code, developed by the Fraunhofer ITWM in recent years. A ..."
Abstract

Cited by 14 (11 self)
 Add to MetaCart
Methods from stochastic geometry allow to construct models which are very good representations of the real complexity of Nonwovens. These realistic models are used as boundaries for a fluid dynamic simulation with a parallel Lattice Boltzmann code, developed by the Fraunhofer ITWM in recent years. As a result, the flow field, the pressure drop across the filter and its permeability are obtained. To study the depth filtration properties, we used a Lagrangian formulation of particle transport in the calculated complex flow field. The relative influence of different filtration mechanisms and the filtration efficiencies of the complex fiber structures are studied as function of particle sizes ranging from D = 2µm. to 4nm. The most penetrating particle size is obtained in good agreement with experiments. For larger particles the clogging of the filter is studied. As an interesting phenomenon, we find often an inhomogeneous loading for particles, even if the particle size is appreciable smaller than typical pore sizes.
Parallel Lattice Boltzmann Methods for CFD Applications
"... The lattice Boltzmann method (LBM) has evolved to a promising alternative to the wellestablished methods based on finite elements/volumes for computational fluid dynamics simulations. Ease of implementation, extensibility, and computational efficiency are the major reasons for LBM’s growing field ..."
Abstract

Cited by 11 (9 self)
 Add to MetaCart
The lattice Boltzmann method (LBM) has evolved to a promising alternative to the wellestablished methods based on finite elements/volumes for computational fluid dynamics simulations. Ease of implementation, extensibility, and computational efficiency are the major reasons for LBM’s growing field of application and increasing popularity. In this paper we give a brief introduction to the involved theory and equations for LBM, present various techniques to increase the singleCPU performance, outline the parallelization of a standard LBM implementation, and show performance results. In order to demonstrate the straightforward extensibility of LBM, we then focus on an application in material science involving fluid flows with free surfaces. We discuss the required extensions to handle this complex scenario, and the impact on the parallelization technique.
Analysis of lattice Boltzmann nodes initialization in Moving Boundary problems
"... Abstract: The lattice Boltzmann method is a numerical scheme based on a fixed grid. Dealing with moving boundary problems, proper routines are needed to initialize the variables at the new nodes, created by the variations of the computational fluid domain. We use the asymptotic analysis to investiga ..."
Abstract

Cited by 6 (0 self)
 Add to MetaCart
Abstract: The lattice Boltzmann method is a numerical scheme based on a fixed grid. Dealing with moving boundary problems, proper routines are needed to initialize the variables at the new nodes, created by the variations of the computational fluid domain. We use the asymptotic analysis to investigate the problem and possible solutions. A simple algorithm is proposed, able to achieve the same accuracy as the standard LBM. The theoretical predictions are tested on simple benchmarks.
Lattice Boltzmann Simulations of 2D Laminar Flows past Two Tandem Cylinders
, 2008
"... We apply the lattice Boltzmann equation (LBE) with multiplerelaxationtime (MRT) collision model to simulate laminar flows in twodimensions (2D). In order to simulate flows in an unbounded domain with the LBE method, we need to address two issues: stretched nonuniform mesh and inflow and outfl ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
We apply the lattice Boltzmann equation (LBE) with multiplerelaxationtime (MRT) collision model to simulate laminar flows in twodimensions (2D). In order to simulate flows in an unbounded domain with the LBE method, we need to address two issues: stretched nonuniform mesh and inflow and outflow boundary conditions. We use the interpolated grid stretching method to address the need of nonuniform mesh. We demonstrate that various inflow and outflow boundary conditions can be easily and consistently realized with the MRTLBE. The MRTLBE with nonuniform stretched grids is first validated with a number of test cases: the Poiseuille flow, the flow past a cylinder asymmetrically placed in a channel, and the flow past a cylinder in an unbounded domain. We use the LBE method to simulate the flow past two tandem cylinders in a unbounded domain with Re = 100. Our results agree well with existing ones. Through this work we demonstrate the effectiveness of the MRTLBE method with grid stretching.
Quantitative analysis of numerical estimates for the permeability of porous media from latticeBoltzmann simulations
 Journal of Statistical Mechanics
, 2010
"... Abstract. During the last decade, latticeBoltzmann simulations have been improved to become an efficient tool for determining the permeability of porous media samples. However, wellknown improvements of the original algorithm are often not implemented. These include, for example, multirelaxation ..."
Abstract

Cited by 5 (1 self)
 Add to MetaCart
(Show Context)
Abstract. During the last decade, latticeBoltzmann simulations have been improved to become an efficient tool for determining the permeability of porous media samples. However, wellknown improvements of the original algorithm are often not implemented. These include, for example, multirelaxation time schemes or improved boundary conditions, as well as different possibilities to impose a pressure gradient. This paper shows that a significant difference of the calculated permeabilities can be found unless one uses a carefully selected setup. We present a detailed discussion of possible simulation setups and quantitative studies of the influence of simulation parameters. We illustrate our results by applying the algorithm to a Fontainebleau sandstone and by comparing our benchmark studies to other numerical permeability measurements in the literature.
A lattice Boltzmann model for diffusion of binary gas mixtures that includes diffusion slip, Int
 J. Numer. Meth. Fluids
"... This thesis describes the development of a Lattice Boltzmann (LB) model for a binary gas mixture. Specifically, channel flow driven by a density gradient with diffusion slip occurring at the wall is studied in depth. The first part of this thesis sets the foundation for the multicomponent model use ..."
Abstract

Cited by 3 (0 self)
 Add to MetaCart
This thesis describes the development of a Lattice Boltzmann (LB) model for a binary gas mixture. Specifically, channel flow driven by a density gradient with diffusion slip occurring at the wall is studied in depth. The first part of this thesis sets the foundation for the multicomponent model used in the subsequent chapters. Commonly used single component LB methods use a nonphysical equation of state, in which the relationship between pressure and density varies according to the scaling used. This is fundamentally unsuitable for extension to multicomponent systems containing gases of differing molecular masses that are modelled with the ideal gas equation of state. Also, existing methods for implementing boundary conditions are unsuitable for extending to novel boundary conditions, such as diffusion slip. Therefore, a new single component LB derivation and a new method for implementing boundary conditions are developed, and validated against Poiseuille flow. However, including a physical equation of state reduces stability and time accuracy, leading to longer computational times, compared with ‘incompressible ’ LB methods. The new method of analysing LB boundary conditions successfully explains observations from other commonly used schemes, such as the slip velocity associated with ‘bounceback’. The new model developed for multicomponent gases avoids the pitfalls of some other LB models, a single computational grid is shared by all the species and the diffusivity is independent of the viscosity. The NavierStokes equation for the mixture and the StefanMaxwell diffusion equation are both recovered by the model. However, the species momentum equations are not recovered correctly and this can lead to instability. Diffusion slip, the nonzero velocity of a gas mixture at a wall parallel to a concentration gradient, is successfully modelled and validated against a simple onedimensional model for channel flow. To increase the accuracy of the scheme a second order numerical implementation is needed. This can be achieved using a variable transformation method which does not result in an increase in computational time.
Coupling of Lattice Boltzmann Equation and Finite Volume Method to Simulate Heat Transfer in a Square Cavity, FDMP:
 Fluid Dynamics & Materials Process.,
, 2009
"... Abstract: The objective of this paper is to assess the effectiveness of the coupled Lattice Boltzmann Equation (LBE) and finite volume method strategy for the simulation of the interaction between thermal radiation and laminar natural convection in a differentially heated square cavity. The vertica ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
Abstract: The objective of this paper is to assess the effectiveness of the coupled Lattice Boltzmann Equation (LBE) and finite volume method strategy for the simulation of the interaction between thermal radiation and laminar natural convection in a differentially heated square cavity. The vertical walls of the cavity are adiabatic, while its top and bottom walls are cold and hot, respectively. The air velocity is determined by the lattice Boltzmann equation and the energy equation is discretized by using a finite volume method. The resulting systems of discretized equations have been solved by an iterative procedure based on a preconditioned conjugate gradient method. Only the surface radiation is taken into account and the walls of the enclosure are assumed to be diffusegrey. The achieved simulations have shown that the coupling between the lattice Boltzmann equation and the finite volume method gives excellent results. It was also observed that the surface radiation standardizes the temperature inside the cavity and causes a considerable increase of the heat transfer.
Addons for Lattice Boltzmann Methods: Regularization, Filtering and Limiters
, 2013
"... We describe how regularization of lattice Boltzmann methods can be achieved by modifying dissipation. Classes of techniques used to try to improve regularization of LBMs include flux limiters, enforcing the exact correct production of entropy and manipulating nonhydrodynamic modes of the system i ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
(Show Context)
We describe how regularization of lattice Boltzmann methods can be achieved by modifying dissipation. Classes of techniques used to try to improve regularization of LBMs include flux limiters, enforcing the exact correct production of entropy and manipulating nonhydrodynamic modes of the system in relaxation. Each of these techniques corresponds to an additional modification of dissipation compared with the standard LBGK model. Using some standard 1D and 2D benchmarks including the shock tube and lid driven cavity, we explore the effectiveness of these classes of methods.