We examine the problem of simulating single and multiphase flow in porous medium systems at the pore scale using the lattice Boltzmann (LB) method. The LB method is a powerful approach, but one which is also computationally demanding; the resolution needed to resolve fundamental phenomena at the pore scale leads to very large lattice sizes, and hence substantial computational and memory requirements that necessitate the use of massively parallel computing approaches. Common LB implementations for simulating flow in porous media store the full lattice, making parallelization straightforward but wasteful. We investigate a two-stage implementation consisting of a sparse domain decomposition stage and a simulation stage that avoids the need to store and operate on lattice points located within a solid phase. A set of five domain decomposition approaches are investigated for single and multiphase flow through both homogeneous and heterogeneous porous medium systems on different parallel computing platforms. An orthogonal recursive bisection method yields the best performance of the methods investigated, showing near linear scaling and substantially less storage and computational time than the traditional approach.

A high-performance lattice Boltzmann implementation to model flow in porous media

Natural convection of hybrid nanofluid heat transport and entropy generation in cavity by using Lattice Boltzmann Method

Paraffin melting is widely applied to the fields of phase
 change materials(PCMs) energy storage, gathering and transportation pipeline
 paraffin removal, etc. Natural convection is the main heat transfer mode
 during paraffin melting, and Ra number is an important factor affecting the
 change of natural convection intensity and Nu number. Nu number variation can
 reflect the influence of natural convection on heat transfer. The
 conventional Nu 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 Ra number on the temperature
 field and flow field of wax in circular tube is analyzed. The heat transfer
 process is reflected by Nu number of moving phase interface. The relation
 between Nu number of moving interface and Nu number of hot wall surface is
 also presented. The results show that the Nu number of moving phase interface
 can reflect the complex nonlinear characteristics of natural convection and
 describe the phase change heat transfer process of wax more accurately.
 Calculation formula of Nu number of moving phase interface and hot wall
 during wax phase change is proposed. Increasing Ra number can quicken the
 melting of wax to meet the actual engineering requirements.

http://www.doiserbia.nb.rs/ft.aspx?id=0354-98362200063Z

Numerical study on Nu number of moving phase interface during wax melting in tube using LBM

In this article, natural alumina/water nanofluid (NF) convection in an isosceles equilateral rhombus-shaped enclosure was simulated using the Simplex algorithm and the control volume method. The enclosure under study had two insulation walls, i.e., a cold wall and a warm wall. Two blades were installed on the warm wall with a temperature equal to that of the warm wall. There was also a fin in the center of the enclosure with a temperature equal to that of the warm wall. The enclosure was horizontally under a magnetic field at Hartmann number (Ha) of 20. The average Nusselt number (Nu), entropy production, Bejan number (Be), and flow and temperature contours were studied while altering the length and thickness of the blades from 0.1 to 0.8 and 0.05 to 0.15, respectively, and the aspect ratio (AR) of the fin from 0.1 to 0.4. The obtained results were then optimized to catch the best results. The two-phase method was used to simulate nanofluid flow. By altering the width and length of the blades and the fin AR, the average Nu varies from 6.52 to 8.31. According to the results, within the range of the above variables, Nu, entropy production, and Be varied from 5.62 to 8.31, 7.55 to 12.36, and 0.48 to 0.6, respectively. 

Analyzing geometric parameters in inclined enclosures filled with magnetic nanofluid using artificial neural networks

Improving heat transfer using nanofluids has proven to be a promising option with many practical applications. However, the behavior of particles conveying energy for thermal transport depends closely on the dimensions of systems and channels where the flow evolves. Thereby, any fine thermal analysis should lean on a mesoscale approach applied at a microscale level. To this end, the multi-distribution functions–thermal lattice Boltzmann method has been taken to deal with convective heat flow and entropy generation in a channel with isothermal top–bottom walls and filled with a nanofluid (Cu/water). It was extended to simulate the flow governed by the Brinkman–Forchheimer Darcy model using the local thermal equilibrium assumption. The effects of nanoparticles’ volume fraction, Darcy number, porosity, heat capacity ratio and thermal conductivity ratio on heat transfer, entropy generation, average Nusselt number, and Bejan number are investigated. Among the salient results, it can be stated that the nanoparticles’ volume fraction increases heat transfer and entropy generation, but such a propensity can be affected by the porous medium permeability used. To sum up, the findings confirm the potential of the multi-distribution functions–lattice Boltzmann formalism to tackle forced nanofluid flows with heat transfer in porous media. 

Simulating Nanofluid Forced Convection Flow by Thermal Lattice Boltzmann Approach

The nanofluid forced convection heat exchange in a porous channel within three heated blocks was numerically investigated using the Nonorthogonal multiple-relaxation time lattice Boltzmann method (...

Zhao Qichen

Papers

Lattice Boltzmann method for nanofluid forced convection heat exchange in a porous channel with multiple heated sources