Table of Contents

• Table of Contents
• About LBfoam
• Highlighted Features
• Directory and Code Structure
• Important Classes
• Installation
  • Run an example
• Getting help and bug report
• Citing this work

About LBfoam

LBfoam is an open-source CFD solver based on the lattice Boltzmann method for foaming simulations. The solver is an extended version of the Palabos library.

The paper presenting this work is published in the Journal of Computer Physics Communications.

Highlighted Features

• 2D/3D Free Surface Lattice Boltzmann (FSLBM) solver
• Coupling of the Navier-Stokes equation and advection-dffisuion equation for the simulation bubble growth
• Implementation of bubble interaction using Piecewise Linear Interface Reconstruction (PLIC) and Ray Tracing algorithms
• Nucleating bubbles based on a nucleation probability field using the Poisson-Disc Sampling algorithm
• Fully-parallelized using the Message Passing Interface (MPI) library

Directory and Code Structure

Figure below shows the directory structure of the LBfoam library.

The algorithms folder contains the PLIC, ray-tracing, Poisson disk-sampling algorithm, and other related functions. The dynamics folder contains the classes for advection-diffusion coupling and applying the Henry's law boundary condition. The bubble folder includes the classes for calculating gas diffusion into each bubble, updating bubble pressures, tracking bubble coalescence, calculation of disjoining pressure, and updating bubbles gas content. The models folder includes a 2D FSLBM model which is not available in Palabos. The directory examples/lbfoam include a variety of demo cases.

lbfoam2D.h and lbfoam3D.h header files provide access to LBfoam classes for 2D and 3D simulations, respectively. Each LBfoam function/class must be called using the namespace called lbfoam (e.g. lbfoam::PLIC2D ).

Important Classes

• lbfoam::PLIC3D: Piecewise Linear Interface Construction method based on Scardovelli and Zaleski for reconsturcting liquid interfaces. This method is used in the calculation of the distance between two adjacent bubbles.

• lbfoam::PLIC2D: 2D implementation of lbfoam::PLIC3D.

• lbfoam::RayTracer3D: Ray tracing algorithm to search for adjacent bubbles. This method is used in the calculation of the disjoining pressure.

• lbfoam::RayTracer2D: 2D implementation of lbfoam::RayTracer3D.

• lbfoam::BubbleGrowth3D: This class implements functionalities to update bubble gas content, and calculate the gas content properly after bubble coalescence, splitting, and formation of new bubbles.

• lbfoam::BubbleGrowth2D: 2D implementation of lbfoam::BubbleGrowth3D.

• lbfoam::BubbleTracking3D: This class implements methods to track bubble motion, coalescence, spliting, etc. as well as calculation of the disjoining pressure between bubbles.

• lbfoam::BubbleTracking2D: 2D implementation of lbfoam::BubbleTracking3D.

• lbfoam::GrowthCoupling3D: This class apply the Henry's law boundary condition on bubble interfaces, and calculates the amount of gas diffused into each bubble that is used in lbfoam::BubbleGrowth3D to update bubble's gas content.

Installation

LBfoam installation is very similar to the Palabos library and it does not depend on any external dependencies. LBfoam uses Scons build tool.

The mandatory packages for installation are gcc (or clang ), make , python3 . For MPI parallel computations, libopenmpi library is required. To output results in .gif format, imagemagick library must be installed.

For Debian based distributions, the following command can install the required libraries.

$ sudo apt install gcc python3 make imagemagick libopenmpi-dev

Similar to Palabos the output of the simulations are in the form of VTK files, which can be visualized using the of Paraview software.

Run an example

First, close the repository using the following git command:

$ git clone https://github.com/mehdiataei/LBfoam.git

Compile the bucket2D example:

$ cd examples/lbfoam/bucket2D
$ make

(Note: To compile the software on MacOS, uncomment the -DPLB_MAC_OS_X compilation flag in the Makefile).

Create tmp folder to store the outputs (the output folder name must be the same as outDir variable in the bucket2D.xml file). Run the example using the following command. The bucket2D.xml contains the simulation parameters.

$ ./bucket2D bucket2D.xml

To run the example in parallel using 8 cores for example:

$ mpirun -np 8 bucket2D bucket2D.xml

results will be stored in tmp folder by default.

Getting help and bug report

Please submit a Github issue, or contact m.ataei@mail.utoronto.ca if you found a bug in the program or needed help with the software.

Citing this work

Please cite the accompanied paper if you intend to use this library in your work.