Lattice Boltzman Method Research Articles

Hybrid numerical methods for modelling multi-physics mass transport in coal

It is a challenging task to predict and analyse the transient flow physics in unconventional complex geological formations such as coal seams. This is due to the multi-scale multi-physics nature of processes taking place in coal seam gas reservoirs. Therefore, numerical tools allowing the incorporation of various flow physics inherent to coal into the simulation routine are of particular importance. At the pore-scale, the rock images obtained by micro-computed tomography are frequently used for flow modelling in porous or fractured media by direct numerical simulations (Lattice Boltzman method or by solving Navier Stokes equations) or by utilising so-called pore-network modelling. Both methods have advantages and drawbacks, while their hybridisation may allow us avoid some of the major pitfalls. Due to a limited number of research dedicated to image-based pore-scale modelling in coal, we develop a hybrid numerical model that combines the Hagen-Poiseuille analytical solution and the volume of fluid advection scheme for fluid flow in fractures with the continuum Darcy flow in the coal matrix. The explicit coupling of fluid flow across the fracture-matrix domains is implemented via corresponding source terms in the governing equations. Besides, additional physics including sorption and matrix swelling-shrinkage phenomena are introduced into the numerical model. The hybrid solver is validated against analytical solutions and a previously developed Darcy-Brinkman-Stokes framework, which has similar functionality for modelling fluid flow in coal seams. To validate the developed model and show its capability to capture multi-scale multi-physics flow in coal, several illustrative simulations are conducted using synthetic and realistic digital images of coal. As a result, the accuracy of the hybrid solver was within 4% when compared to the Darcy-Brinkman-Stokes framework for flow simulation on realistic geometry. Besides, the non-parallelised hybrid model outperformed the parallelised direct numerical simulation, being more than 90 times faster in terms of computational time. The findings are beneficial for conducting larger core-scale simulations of multi-scale multi-physics flow in coal seams with potential applications to natural gas production, hydrogen storage, and carbon dioxide geosequestration.

Numerical study on Nusselt number of moving phase interface during wax melting in tube using lattice Boltzman method

Paraffin melting is widely applied to the fields of PCM energy storage, gathering and transportation pipe-line paraffin removal, etc. Natural-convection is the main heat transfer mode during paraffin melting, and Rayleigh number is an important factor affecting the change of natural-convection intensity. Nusselt number variation can reflect the influence of natural-convection on heat transfer. The conventional Nusselt number of hot wall surface reflects only the convective heat transfer intensity of the fixed wall, while it does not take into account that the phase change interface has the characteristics of moving in the phase change process. A double distribution model of paraffin phase transformation in circular tube based on lattice Boltzmann method is established in this paper. The influence of Rayleigh number on the temperature field and flow field of wax in circular tube is analyzed. The heat transfer process is reflected by Nusselt number of moving phase interface. The relation between Nusselt number of moving interface and Nusselt number of hot wall surface is also presented. The results show that the Nusselt number of moving phase interface can reflect the complex non-linear characteristics of natural-convection and describe the phase change heat transfer process of wax more accurately. Calculation formula of Nusselt number of moving phase interface and hot wall during wax phase change is proposed. Increasing Rayleigh number can quicken the melting of wax to meet the actual engineering requirements.

Double Diffusive Convection of Power Law Fluids Through Taylor–Couette Flow

The proposed study focuses on the effect of double diffusive convection on the flow structures of power-law fluids between two coaxial cylinders of finite aspect ratios with end caps. We adopted a D2Q9 axisymmetric lattice Boltzmann model to predict the power-law fluid flow and D2Q4 (Lattice Boltzman method) model for azimuthal velocity, concentration, and the temperature. For ( is the solutal and thermal buoyancy forces ratio), fixed Taylor number with increasing Rayleigh number , the thermal base flow regime is more pronounced for the pseudoplastic fluid compared to the dilatant fluid. In addition, the thermal base flow in the annulus is delayed when increases. Thus, the increase of the behavior index has a stabilizing effect on the flow structure. On the other hand, when , the solute buoyancy forces in the annulus prevail over the centrifugal and thermal buoyancy forces, and the flow becomes ultimately a solute base flow for . For , the flow becomes a thermal base flow for . Thus, the mass transfer with negative values has a greater stabilizing effect on the flow structures than with positive .

Using the lattice Boltzman method and GPU computing to model flow in organ pipes

The lattice Boltzman method (LBM) has been used to study oscillating air flow in musical instruments since the early 1990s. Most of the work has focused on flow into organ pipes and flow behavior around the instrument’s labium. The current work intends to use GPU computing to simulate oscillations in 3D modeled and printed organ pipes of different cross-sectional geometries. These pipes will be used in experimental validation measurements of flow at the pipe exit (see TCMU general session for this work). The domain space required to visualize each outlet of air (around the labium and the pipe’s open end) simultaneously with a sufficient resolution was larger than could fit in our GPU's memory. The resolution and space requirements of the simulations has required the use of high-memory GPUs (a physical machine as well as Google Cloud GPU have been tested). The physical and computational parameter optimization, GPU processes, and the simulation difficulties encountered will be discussed. Finally, preliminary comparisons between experiment and model will be shared.

Analysis of the Structure and Hydraulic Function of Bordered Pits Using the Lattice Boltzman Method

Fluid flow between adjacent tracheids is realized through bordered pits in the xylem of conifers. The pit has an extremely small size and a highly complex structure. This paper presents a mesoscopic analytical method for the relationship between the pit structure and its hydraulic characteristics through mathematical modeling using the lattice Boltzmann method (LBM) and curved boundary treatment. Mongolian Scots pine were selected as the research subject of this study, and the bordered pit structure parameters was collected by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the original geometric features were maintained for direct modeling analysis. The model revealed the relationship between various components of the bordered pit and liquid flow velocity/resistance, indicating that margo is the main factor affecting flow resistance. Further anatomical investigation separately analyzed the influence of change in a single factor, including pit diameter, pit aperture diameter, pit depth, torus diameter, and margo thickness, on the overall flow and pressure drop to confirm the importance of various factors in this relationship. Additionally, the influence of pore size and pore location distribution in the margo on the flow rate and pressure drop was further analyzed quantitatively. The results showed that the flow rate through individual pores is the result of the combined effect of pore area and radial position of the pore in the margo. Our study promotes the research and application of the mesoscopic model LBM in simulating flow conditions in the complex flow field of pits, which realizes the numerical analysis of the flow field model based on individualized real bordered pits. In comparison with the classical macroscopic model, the accuracy and effectiveness of the proposed model are proved. This research can provide a promising method for analyzing the physiological and ecological functions of conifer and realizing the efficient utilization of wood resources.

Numeric Study on Skin Friction Reduction of Engine Oil-WS2 Nanofluid by MRT Lattice Boltzman Method

Numeric Study on Skin Friction Reduction of Engine Oil-WS2 Nanofluid by MRT Lattice Boltzman Method

Simulation of three‐dimensional incompressible flows in generalized curvilinear coordinates using a high‐order compact finite‐difference lattice Boltzmann method

SummaryIn the present study, a high‐order compact finite‐difference lattice Boltzmann method is applied for accurately computing 3‐D incompressible flows in the generalized curvilinear coordinates to handle practical and realistic geometries with curved boundaries and nonuniform grids. The incompressible form of the 3‐D nineteen discrete velocity lattice Boltzmann method is transformed into the generalized curvilinear coordinates. Herein, a fourth‐order compact finite‐difference scheme and a fourth‐order Runge‐Kutta scheme are used for the discretization of the spatial derivatives and the temporal term, respectively, in the resulting 3‐D nineteen discrete velocity lattice Boltzmann equation to provide an accurate 3‐D incompressible flow solver. A high‐order spectral‐type low‐pass compact filtering technique is applied to have a stable solution. All boundary conditions are implemented based on the solution of the governing equations in the 3‐D generalized curvilinear coordinates. Numerical solutions of different 3‐D benchmark and practical incompressible flow problems are performed to demonstrate the accuracy and performance of the solution methodology presented. Herein, the 2‐D cylindrical Couette flow, the decay of a 3‐D double shear wave, the cubic lid‐driven cavity flow with nonuniform grids, the flow through a square duct with 90° bend and the flow past a sphere at different flow conditions are considered for validating the present computations. Numerical results obtained show the accuracy and robustness of the present solution methodology based on the implementation of the high‐order compact finite‐difference lattice Boltzman method in the generalized curvilinear coordinates for solving 3‐D incompressible flows over practical and realistic geometries.

An immersed boundary method for computational simulation of red blood cell in poiseuille flow

In this paper, the effects of Red Blood Cell hardness in a viscous incompressible flow is investigated. The effects of hardness changes on the membrane behavior and its around flow is studied. The Lattice Boltzman method is used for solving the flow field and the Immersed Boundary method is used for membrane motion simulation. The relation between them is done using Dirac Delta function. In the Immersed Boundary method the elastic membrane is modeled in Lagrangian coordinate but the flow field is discretized using a uniform and fixed Eulerian grid. When RBCs have less elastic properties; they pass the obstacle hardly and increase the pressure of around flow.Velocity decrease due to existance of RBC with low flexibility results in increase of pressure around the RBC. This pressure increase due to stiffness of RBC membrane can be seen in anemia and heart diseases. The translational speed of a RBC decreases as its elasticity modulus increases The comparison between the present results and other available results show that the Lattice Boltzmann and Immersed Boundary methods have good capability for modeling of immersed objects motions.DOI: http://dx.doi.org/10.5755/j01.mech.24.3.18063

Toward multiscale modelings of grain-fluid systems

Computationally efficient methods have been developed for simulating partially saturated granular materials in the pendular regime. In contrast, one hardly avoid expensive direct resolutions of 2-phase fluid dynamics problem for mixed pendular-funicular situations or even saturated regimes. Following previous developments for single-phase flow, a pore-network approach of the coupling problems is described. The geometry and movements of phases and interfaces are described on the basis of a tetrahedrization of the pore space, introducing elementary objects such as bridge, meniscus, pore body and pore throat, together with local rules of evolution. As firmly established local rules are still missing on some aspects (entry capillary pressure and pore-scale pressure-saturation relations, forces on the grains, or kinetics of transfers in mixed situations) a multi-scale numerical framework is introduced, enhancing the pore-network approach with the help of direct simulations. Small subsets of a granular system are extracted, in which multiphase scenario are solved using the Lattice-Boltzman method (LBM). In turns, a global problem is assembled and solved at the network scale, as illustrated by a simulated primary drainage.

Performance Analysis of 2D and 3D Fluid Flow Modelling Using Lattice Boltzmann Method

Several studies have been conducted to observe properties of fluid flow in materials using the Lattice Boltzman Method (LBM). There are two widely used lattice model, the D2Q9 for the 2D simulation, and the D3Q19 for the 3D simulation. Our particular interest is to study the velocity map both using the 2D and the 3D simulation, using the same object. The aim of this study is to evaluate effectiveness and efficiency of both methods. In our simulation, the velocity profile between the 2D and 3D models differs greatly (mean error 30.4%) if the object has complex lateral structure (the shape along the z-axes differs greatly), while for the less complex object, the profile has only 1.4% of mean error. The computing time for the 3D model took 13 times longer than the simulation of the 2D model. The result from the comparison of both methods concludes that the simplification of fluid flow simulation of 3D objects into 2D objects should be taken carefully, for in some cases, the simplification is not quite appropriate.

Computational model of simulation for mechanics of biofluids using the generalized lattice boltzman method

A 3D model for the numerical simulation of artificial aortic prostheses is presented, considering fluid-structure interaction. The method is based in the General Lattice Boltzmann equation under a multi-relaxation scheme. Stream lines, velocities and shear stresses inside the biological fluid are reported and discussed. Technical details of the algorithm are also described. As well, an algorithm for the LB mesh generation is presented and evaluated. Numerical results of artificial heart valves in aortic position are reported here, showing the versatility of the proposed approach.

Pressure-strain energy redistribution in compressible turbulence: return-to-isotropy versus kinetic-potential energy equipartition

Return-to-isotropy and kinetic-potential energy equipartition are two fundamental pressure-moderated energy redistributive processes in anisotropic compressible turbulence. Pressure-strain correlation tensor redistributes energy among various Reynolds stress components and pressure-dilatation is responsible for energy reallocation between dilatational kinetic and potential energies. The competition and interplay between these pressure-based processes are investigated in this study. Direct numerical simulations (DNS) of low turbulent Mach number dilatational turbulence are performed employing the hybrid thermal Lattice Boltzman method (HTLBM). It is found that a tendency towards equipartition precedes proclivity for isotropization. An evolution towards equipartition has a collateral but critical effect on return-to-isotropy. The preferential transfer of energy from strong (rather than weak) Reynolds stress components to potential energy accelerates the isotropization of dilatational fluctuations. Understanding of these pressure-based redistributive processes is critical for developing insight into the character of compressible turbulence.

Heat Transfer in Hot Pressing of Saturated Fiber Suspensions

This paper presents a three-dimensional numerical framework based on lattice Boltzman method combined with the energy equation for predicting the thermal properties of saturated fiber networks. Heat transfer in fiber suspensions during hot pressing in paper making process is investigated. The effects of efficient preheating on overall energy savings are discussed. The accuracy of the analytical solution based on the assumption of semi-infinite solid body is also investigated. The results show that the thermal properties change significantly depending on the wood fiber types. The effective thermal conductivities of fiber suspensions for three different fiber types are calculated. The predictions compare well with existing experimental and analytical data.

Simulation of Non-Newtonian Blood Flow by Lattice Boltzman Method

Blood flow under various conditions of vessel is simulated as a non-Newtonian fluid by the two-dimensional Lattice Boltzmann method, in which the Casson model is used to express the relationship between viscosity and shear rate of the blood. The flow field distributions at certain sites near the narrowing and bifurcation of the vessel explain the hemodynamic mechanism of the predilection of the atherosclerotic lesions for these sites which are consistent with that found by medical studies.

Lattice Boltzman Method Simulation of Aeroacoustics and Nonreflecting Boundary Conditions

A lattice Boltzmann method that can recover the first coefficient of viscosity and the specific heat ratio correctly has been adopted for one-step aeroacoustic simulations because it can recover the speed of sound correctly. Instead of solving the Navier-Stokes equations as in the case of direct numerical simulation, the lattice Boltzmann method only needs to solve one transport equation for the collision function. Other flow properties are obtained by integrating this collision function over the particle velocity space. The lattice Boltzmann method is effective only if appropriate nonreflecting boundary conditions for open computational boundaries are available, just like the direct numerical simulation. Four different nonreflecting boundary conditions are commonly used with direct numerical simulation for one-step aeroacoustic simulations. Among these are the characteristics-based method, the perfectly matched layer method, the C 1 continuous method, and the absorbing layer method. Not all nonreflecting boundary conditions are applicable when used with the lattice Boltzmann method; some might not be appropriate, whereas others could be rather effective. This paper examines some existing nonreflecting boundary conditions plus other new proposals, their appropriateness, and their suitability for the lattice Boltzmann method. The assessment is made against two classic aeroacoustic problems: propagation of a plane pressure pulse and propagation of acoustic, entropy, and vortex pulses in a uniform stream. A reference solution is obtained using direct numerical simulation assuming a relatively large computational domain without any specified nonreflecting boundary conditions. The results, obtained with a computational domain half the size of that used for the direct numerical simulation calculations, show that the absorbing layer method and the extrapolation method with assumed filter perform the best.

Simulation of binary mixtures with the lattice Boltzman method

A lattice Boltzman model for the simulation of binary mixtures is presented. Contrary to previous models, the present formulation is able to simulate mixtures with different Schmidt numbers and arbitrary molecular mass ratio of the components. In the hydrodynamic limit, the Navier-Stokes and the Stefan-Maxwell binary diffusion equations are recovered. The model is used for the simulation of binary diffusion and mixing layers. The results are found to be in good agreement with a derived similarity solution and with the predictions of a transient spectral element code.

G1103 圧力波を駆動源とする船舶用推進ノズル内気液二相流の数値的研究(2)(GS-11 気液二相流,一般セッション)

We had proposed a propulsive nozzle for a ship with a pulse detonation engine. The high-pressure wave generated by the PDE is used as a source of a drive. In addition to the experimental analysis, we try to analize the flows inside the propulsive nozzle numerically. The new two particles model of a thermal finite difference lattice Boltzman method is presented for simulating gas-liquid two phase flows like air-water flows. The model enables us to control the sound speed of each phase by introducing the macroscopic effects to the FDLBM as the intermolecular force. It is confirmed that the Rankine-Hugoniot relation of ideal gases is satisfied in the gas phase, the sound speed agrees with the macroscopic equation, and the incompressible effect is given to the liquid phase.

On implementation of the finite difference lattice boltzmann method with internal degree of freedom to edgetone

The lattice Boltzman method (LBM) and the finite difference-based lattice Boltzmann method (FDLBM) are quite recent approaches for simulating fluid flow, which have been proven as valid and efficient tools in a variety of complex flow problems. They are considered attractive alternatives to conventional finite-difference schemes because they recover the Navier-Stokes equations and are computationally more stable, and easily parallelizable. However, most models of theLBM orFDLBM are for incompressible fluids because of the simplicity of the structure of the model. Although some models for compressible thermal fluids have been introduced, these models are for monatomic gases, and suffer from the instability in calculations. A lattice BGK model based on a finite difference scheme with an internal degree of freedom is employed and it is shown that a diatomic gas such as air is successfully simulated. In this research we present a 2-dimensional edge tone to predict the frequency characteristics of discrete oscillations of a jet-edge feedback cycle by theFDLBM in which any specific heat ratio γ can be chosen freely. The jet is chosen long enough in order to guarantee the parabolic velocity profile of a jet at the outlet, and the edge is of an angle of α=23°. At a stand-off distancew, the edge is inserted along the centerline of the jet, and a sinuous instability wave with real frequency is assumed to be created in the vicinity of the nozzle exit and to propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations resulting from periodic oscillation of the jet around the edge.

格子ボルツマン法を用いた血栓予測法(OS8-1人工臓器内の流れ1)

格子ボルツマン法を用いた血栓予測法(OS8-1人工臓器内の流れ1)

格子ボルツマン法による二相流の乱流解析(熱流体解析技術の新展開-格子ボルツマン法-,F06 熱工学部門企画)

格子ボルツマン法による二相流の乱流解析(熱流体解析技術の新展開-格子ボルツマン法-,F06 熱工学部門企画)