We present the OpenLB package, a C++ library providing a flexible framework for lattice Boltzmann simulations. The code is publicly available and published under GNU GPLv2, which allows for adaption and implementation of additional models. The extensibility benefits from a modular code structure achieved e.g. by utilizing template meta-programming. The package covers various methodical approaches and is applicable to a wide range of transport problems (e.g. fluid, particulate and thermal flows). The built-in processing of the STL file format furthermore allows for the simple setup of simulations in complex geometries. The utilization of MPI as well as OpenMP parallelism enables the user to perform those simulations on large-scale computing clusters. It requires a minimal amount of dependencies and includes several benchmark cases and examples. The package presented here aims at providing an open access platform for both, applicants and developers, from academia as well as industry, which facilitates the extension of previous implementations and results to novel fields of application for lattice Boltzmann methods. OpenLB was tested and validated over several code reviews and publications. This paper summarizes the findings and gives a brief introduction to the underlying concepts as well as the design of the parallel data structure.

https://publikationen.bibliothek.kit.edu/1000120568/85144642

OpenLB—Open source lattice Boltzmann code

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pol.20210555

Chemically specific coarse-graining of polymers: Methods and prospects

Total enthalpy-based lattice Boltzmann simulations of melting in paraffin/metal foam composite phase change materials

Pore-scale convection-conduction heat transfer and fluid flow in open-cell metal foams: A three-dimensional multiple-relaxation time lattice Boltzmann (MRT-LBM) solution

Due to reduced thermal conductivity, vacuum insulation panels (VIPs) provide significant thermal insulation performance. Our novel vacuum panels operate at reduced pressure and are filled with a powder of precipitated silicic acid to further hinder convection and provide static stability against atmospheric pressure. To obtain an in depth understanding of heat transfer mechanisms, their interactions and their dependencies inside VIPs, detailed microscale simulations are conducted. Particle characteristics for silica are used with a discrete element method (DEM) simulation, using open source software Yade-DEM, to generate a periodic compressed packing of precipitated silicic acid particles. This aggregate packing is then imported into OpenLB (openlb.net) as a fully resolved geometry, and used to study the effects on heat transfer at the microscale. A three dimensional Lattice Boltzmann method (LBM) for conjugated heat transfer is implemented with open source software OpenLB, which is extended to include radiative heat transport. The infrared intensity distribution is solved and coupled with the temperature through the emissivity, absorption and scattering of the studied media using the radiative transfer equation by means of LBM. This new holistic approach provides a distinct advantage over similar porous media approaches by providing direct control and tuning of particle packing characteristics such as aggregate size, shape and pore size distributions and studying their influence directly on conduction and radiation independently. Our aim is to generate one holistic tool which can be used to generate silica geometry and then simulate automatically the thermal conductivity through the generated geometry.

Conjugate heat transfer through nano scale porous media to optimize vacuum insulation panels with lattice Boltzmann methods

A 3D Lattice Boltzmann method for light simulation in participating media

The numerical prediction of radiative transport is a challenging task due to the complexity of the radiative transport equation. We apply the lattice Boltzmann method (LBM), originally developed for fluid flow problems, to solve the radiative transport in volume. One model (meso RTLBM) is derived directly from a discretization of the radiative transport equation, yielding in a precise but numerical costly scheme. The second model (macro RTLBM) solves the Helmholtz equation, which is a proper approximation for highly scattering volumes. Both numerical algorithms are validated against Monte–Carlo data for a set of 35 optical parameters, which correspond to radiative transport ranging from ballistic to diffuse regimes. Together with a set of four benchmark simulations, the comprehensive validation concludes the overall quality and detects asymptotic trends for radiative transport LBM. Furthermore, an accuracy map is presented, which summarizes the error for all parameters. This graph allows to determine the validity range for both radiative transport LBM at a glance. Finally, comprehensive guidelines are formulated to facilitate the choice of the radiative transport LBM model.

Radiative transfer lattice Boltzmann methods: 3D models and their performance in different regimes of radiative transfer

OpenLB Release 1.3: Open Source Lattice Boltzmann Code

The design and optimization of photobioreactors (PBR) can benefit from the development of robust and yet quantitatively accurate computational models, that incorporate the complex interplay of fundamental phenomena. At a minimum, the simulation model requires at least three submodels for hydrodynamic, light supply and biomass kinetics as pointed out by various review articles on computational fluid flow models for PBR design. By modeling the hydrodynamics, the light-dark-cycles can be detected and the mixing characteristic of the flow besides its mass transport is analyzed. The radiative transport model is deployed to predict the local light intensities according to wavelength of the light and scattering characteristic of the culture. The third submodel implements the biomass growth kinetic, by coupling the local light intensities to hydrodynamic information of CO2 concentration, to predict the algal growth. The developed mesoscopic simulation model is applied to a tubular PBR with transparent walls and internal sponge structure. The complex hydrodynamics and the homogeneous illumination in such reactors is very promising for CFD based optimization.

Albert Mink

Papers

OpenLB—Open source lattice Boltzmann code

A 3D Lattice Boltzmann method for light simulation in participating media

Radiative transfer lattice Boltzmann methods: 3D models and their performance in different regimes of radiative transfer

OpenLB Release 1.3: Open Source Lattice Boltzmann Code

Comprehensive computational model for coupled fluid flow, mass transfer and light supply in tubular photobioreactors equipped with glass sponges