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Category: News

First OpenLB Hackathon completed

From October 6-11, 2024, the LBRG successfully organized the first OpenLB Hackathon in Feldberg, Germany. For one week, 14 group members focused on core development to further improve OpenLB in terms of boundary condition modeling, GPU support and user friendliness.

New Video on the Settling Behavior of Particle Swarms

We have just released a new video on our OpenLB YouTube Channel:

Particle Swarm Settling Behavior Spheres and Cubes Using Lattice Boltzmann Methods and OpenLB

This video presents a detailed comparison of the swarm settling (or hindered settling) behavior of volume-equivalent spheres and cubes. The simulation is fully resolved and four-way coupled, showing the dynamic behavior of 1934 particles within a triple periodic domain measuring 15D x 15D x 15D, where D = 3 mm is the diameter of the spheres. The particle volume fraction is approximately 30% and the Archimedes number is set to 2000.

Observations from the video

  • Shape matters: Particle shape has a significant effect on the suspension dynamics.
  • Average settling velocity: Cubes settle on average approximately 24% slower than the volume-equivalent spheres.
  • Clustering: Spheres have a higher tendency to form clusters than cubes.

The simulations were performed with OpenLB using 152 cores (Intel Xeon Platinum 8368 CPU) and both simulations together took less than 13 hours to complete.

Further details and in-depth analysis can be found in the corresponding publications [1, 2].

[1]: J. E. Marquardt, N. Hafen, and M. J. Krause, “A novel model for direct numerical simulation of suspension dynamics with arbitrarily shaped convex particles,” Computer Physics Communications, vol. 304, p. 109321, 2024, doi: 10.1016/j.cpc.2024.109321.

[2]: J. E. Marquardt, N. Hafen, and M. J. Krause, “A novel particle decomposition scheme to improve parallel performance of fully resolved particulate flow simulations,” Journal of Computational Science, vol. 78, p. 102263, 2024, doi: https://doi.org/10.1016/j.jocs.2024.1….

For further information please visit the associated show case: Particle Swarm Sedimentation

New Video on our upcoming Fluid Structure Interaction module

We have just released a new video on our OpenLB YouTube Channel:

OpenLB Development Preview: Large Eddy Lattice Boltzmann Simulation of a Wind Park

This is a first experimental showcase of OpenLB’s upcoming general purpose fluid structure interaction (FSI) capabilities. Visualized are various viewpoints on the vorticity norm of a two-way coupled four-turbine wind park setup with Reynolds number 1.2 Million. The simulation consisting of 1.5 billion cells utilized a single accelerated compute node of 4x NVIDIA H100 GPGPUs.

Computed on HoreKa Teal at KIT, the world’s sixth most energy efficient supercomputer.

Simulation & Visualization by Adrian Kummerländer

Visualization was generated in ParaView.

Website Update: Showcase Section Launched

We are excited to announce the launch of a new section dedicated to showcasing OpenLB projects! This section features a variety of innovative and practical applications, demonstrating the powerful capabilities of OpenLB in computational fluid dynamics. Explore detailed project descriptions, and visual simulations that highlight the versatility and effectiveness of OpenLB in solving real-world problems. Visit the new Showcase section today and get inspired by the possibilities with OpenLB! Click here to explore.

LBM Spring School in Heidelberg successfully finished

The executive committee is happy to announce the closing of the 7th LBM Spring School with OpenLB Software Lab. We hosted 57 participants from 13 countries this year. Congratulations to Jakob Scheel from the US for winning our poster award. We are already busy with organizing the next spring schools. The 8th spring school is planned to take place in Marseille, France from May 19-23, 2025. We would like to thank all participants for attending the 7th spring school in Heidelberg and acknowledge the support from our funders.

On behalf of the spring school executive committee (Kerstin Dick, Shota Ito, Mathias J. Krause and Stephan Simonis)

OpenLB Release 1.7 available for download

The developer team is very happy to announce the release of the next version of OpenLB. The updated open-source Lattice Boltzmann (LB) code is now available for download.

Major changes include the adaptation of many existing models into the GPU-supporting operator style, a validated turbulent velocity inlet condition and a special focus on new multi phase and particle models. This is augmented by a collection of bugfixes and general usability improvements.

For the first time, the new release is also available in a new public Git repository together with all previous releases. We encourage everyone to submit contributions as merge requests and report issues there.

Core development continues within the existing private repository which is available to consortium members.

Release notes

New features and improvements

  • Many existing models converted to the operator-style (“GPU support”)
  • New multi phase models, interaction potentials and examples
  • New Unit Converter for multi phase simulations
  • New validated turbulent inlet condition Vortex Method
  • New particle decomposition scheme that improves parallel performance of fully resolved particulate flow simulations using HLBM
  • New boundary condition zero gradient
  • Tidy up, (performance) improvements of optimization code
  • Optional support for loading porosity data using OpenVDB voxel volumes

New examples

  • multiComponent/airBubbleCoalescence3d
  • multiComponent/waterAirflatInterface2d
  • advectionDiffusionReaction/longitudinalMixing3d
  • advectionDiffusionReaction/convectedPlate3d
  • porousMedia/city3d
  • porousMedia/resolvedRock3d

Examples with full GPU support

  • turbulence/tgv3d
  • turbulence/nozzle3d
  • turbulence/venturi3d
  • turbulence/aorta3d
  • laminar/poiseuille(2,3)d
  • laminar/poiseuille(2,3)dEoc
  • laminar/cylinder(2,3)d
  • laminar/bstep(2,3)d
  • laminar/cavity(2,3)d
  • laminar/cavity3dBenchmark
  • laminar/testFlow3dSolver
  • laminar/powerLaw2d
  • laminar/cavity2dSolver
  • multiComponent/fourRollMill2d
  • multiComponent/rayleighTaylor3d
  • multiComponent/youngLaplace3d
  • multiComponent/binaryShearFlow2d
  • multiComponent/microFluidics2d
  • multiComponent/contactAngle(2,3)d
  • multiComponent/phaseSeparation(2,3)d
  • multiComponent/rayleighTaylor2d
  • multiComponent/airBubbleCoalescence3d
  • multiComponent/waterAirflatInterface2d
  • multiComponent/youngLaplace2d
  • advectionDiffusionReaction/advectionDiffusion(1,2,3)d
  • advectionDiffusionReaction/convectedPlate3d
  • thermal/squareCavity2d
  • thermal/porousPlate(2,3)d
  • thermal/squareCavity3d
  • thermal/rayleighBenard(2,3)d
  • porousMedia/city3d
  • porousMedia/resolvedRock3d
  • freeSurface/fallingDrop(2,3)d
  • freeSurface/breakingDam(2,3)d
  • freeSurface/rayleighInstability3d
  • freeSurface/deepFallingDrop2d

Citation

If you want to cite OpenLB 1.7 you can use:

A. Kummerländer, T. Bingert, F. Bukreev, L. Czelusniak, D. Dapelo, N. Hafen, M. Heinzelmann, S. Ito, J. Jeßberger, H. Kusumaatmaja, J.E. Marquardt, M. Rennick, T. Pertzel, F. Prinz, M. Sadric, M. Schecher, S. Simonis, P. Sitter, D. Teutscher, M. Zhong, and M.J. Krause.

OpenLB Release 1.7: Open Source Lattice Boltzmann Code.

Version 1.7. Feb. 2024.

DOI: 10.5281/zenodo.10684609

General metadata is also available as a CITATION.cff file following the standard Citation File Format (CFF).

Supported Systems

OpenLB is able to utilize vectorization (AVX2/AVX-512) on x86 CPUs [1] and NVIDIA GPUs for block-local processing. CPU targets may additionally utilize OpenMP for shared memory parallelization while any communication between individual processes is performed using MPI.

It has been successfully employed for simulations on computers ranging from low-end smartphones over multi-GPU workstations up to supercomputers and even runs in your browser.

The present release has been explicitly tested in the following environments:

  • Red Hat Enterprise Linux 8.x (HoreKa, BwUniCluster2)
  • NixOS 22.11, 23.11 and unstable (Nix Flake provided)
  • Ubuntu 20.04 and newer
  • Windows 10, 11 via WSL
  • Mac OS Ventura 13.6.3

[1]: Other CPU targets are also supported, e.g. common Smartphone ARM CPUs and Apple M1/M2.

New Android App “paint2sim” Released

Introducing the app “paint2sim” – A Digital Twin for 2D Fluid Flow Simulations

Paint2sim is a mobile application using a Lattice Boltzmann Method realized by the open-source simulation framework OpenLB. This innovative app allows users to scan hand-drawn domains and visualize 2D fluid flow simulations just-in-time on their mobile devices. Whether you’re a student, researcher, or engineer, explore fluid dynamics with an intuitive interface with your fingertips. The app is freely available for download.

For in-depth technical insights, refer to our latest paper, “Just-in-Time Fluid Flow Simulation on Mobile Devices Using OpenVisFlow and OpenLB

Dennis Teutscher and his team developed the app paint2sim as part of the “teaching4future” project, with funding from the Lattice Boltzmann Research Group at KIT and the Ministry of Science, Research, and Arts of Baden-Württemberg, Germany.

Use Case: Scanning a hand-drawn domain and simulating it on a mobile device

OpenLB Community YouTube Channel Update

We have just released a new video on our OpenLB YouTube Channel:

Heterogeneous Load Balancing in OpenLB: Cooperatively Utilizing CPUs and GPUs for a Turbulent Mixing Simulation

Following up on the turbulent micromixer simulation showcased here, the present video illustrates OpenLB’s heterogeneous computation capabilities.

The performance of the simulation case is improved by up to 87% when using heterogeneous CPU-GPU based compared to GPU-only execution. This is achived by distributing the two computationally expensive turbulent inlet regions onto CPUs while the comparatively cheaper bulk regions are processed on GPUs. The underlying inhomogeneous spatial domain decomposition was obtained using a novel genetic algorithm for cost-aware optimization.

A single accelerated CPU-GPU node of the HoreKa supercomputer (2x Intel Xeon Platinum 8368, 4x NVIDIA A100) was used for the showcased simulation consisting of 355 million lattice cells.
OpenLB enabled the cooperative usage of MPI, OpenMP, AVX-512 vectorization and CUDA, reaching a throughput of ~19.25 billion (NSE-only) resp. ~4.79 billion cell updates per second for the fully coupled case.

Simulation setup: Fedor Bukreev
Heterogeneous Load Balancing, Performance engineering, Visualization: Adrian Kummerländer

For further information please visit the associated show case: Heterogeneous Load Balancing

7th Spring School in Heidelberg (Germany) 2024  – Register Now

Registration is now open for the Seventh Spring School on Lattice Boltzmann Methods with OpenLB Software Lab that will be held in Heidelberg/Germany from 4th to 8th of March 2024. The spring school introduces scientists and applicants to the theory of Lattice Boltzmann Methods (LBM) and trains them on practical problems.

Option B: The first half of the week is dedicated to theoretical fundamentals up to ongoing research on selected topics in kinetic theory, scientific computing, LBM, and Partial Differential Equations. Followed by mentored training on case studies using OpenLB in the second half of the week. Emphasis is placed on the modelling and simulation of particulate, multi-component, and turbulent fluid flows.

Option A: Advanced OpenLB users and developers are enabled to solve their own application problems and implement their own solution approaches. All participants benefit from knowledge exchange during the poster session, coffee breaks, and the excursion. We look forward to your participation.

Keep in mind that the number of participants is limited and that the registration follows a first come first serve principle.

On behalf of the spring school executive committee, Kerstin Dick, Shota Ito, Mathias J. Krause, Stephan Simonis