About

FLEXI is a high-order numerical framework for solving PDEs, with a special focus on Computational Fluid Dynamics. FLEXI is based on the Discontinuous Galerkin Spectral Element Method (DGSEM), which allows for high-order of accuracy and fully unstructured hexahedral meshes. The solver is parallelized very efficiently for large-scale applications and scales to 500,000+ cores. Moreover, FLEXI comes with a capable pre- and postprocessing suite that enables complex simulation setups up to the finished visualization.

FLEXI has been developed by the Numerics Research Group (NRG) founded by Prof. Claus-Dieter Munz and currently lead by Prof. Andrea Beck at the Institute of Aerodynamics and Gasdynamics at the University of Stuttgart, Germany.

You can find detailed installation instructions, the extensive documentation and several tutorial cases for FLEXI here.

Numerous people have worked on and with FLEXI over the last years. We would like to thank all these contributors for their efforts they spent on building FLEXI.

In case you have questions regarding FLEXI or want to contribute yourself by either reporting bugs, requesting features or adding somthing different to the project, feel free to open an issue or pull request.

Cite

FLEXI is a scientific project. If you use FLEXI for publications or presentations in science, please support the project by citing it. As general reference, please cite

Krais, N., Beck, A., Bolemann, T., Frank, H., Flad, D., Gassner, G., Hindenlang, F., Hoffmann, M., Kuhn, T., Sonntag, M., Munz, C.-D.
FLEXI: A high order discontinuous Galerkin framework for hyperbolic–parabolic conservation laws,
Computers & Mathematics with Applications, 81, (2021) 186-219

or use the following Bibtex files

@article{flexi,
  title = {{FLEXI}: {A} high order discontinuous {G}alerkin framework for hyperbolic-parabolic conservation laws},
  journal = {Computers \& Mathematics with Applications},
  volume = {81},
  pages = {186-219},
  year = {2021},
  doi = {https://doi.org/10.1016/j.camwa.2020.05.004},
  author = {Nico Krais and Andrea Beck and Thomas Bolemann and Hannes Frank and David Flad and Gregor Gassner and Florian Hindenlang and Malte Hoffmann and Thomas Kuhn and Matthias Sonntag and Claus-Dieter Munz},
}

To refer to specific applications and features, you can also cite the appropriate paper from this list.

Quick Start Guide

For a more detailed installation instructions, please see the documention here.

FLEXI is tested for various Linux distributions including Ubuntu, OpenSUSE, CentOS or Arch and also runs on MacOS. For installation you require the following dependencies:

Package	Required	Installed by FLEXI
Git	x
CMake	x
C/C++ Compiler	x
Fortran Compiler	x
LAPACK	x	x
HDF5	x	x
MPI	(x)

The MPI library is only required for running parallel simulations on multiple ranks and the HDF5 and LAPACK libraries can be installed automatically during the FLEXI build process. The names of the packages and the package manager might differ depending on the specific distribution used.

Getting the code

Open a terminal, download FLEXI via git and optionally export the FLEXI directory:

git clone https://github.com/flexi-framework/flexi.git
export FLEXI_DIR="$(pwd)/flexi"

Compiling the code

Enter the FLEXI directory, create a build directory and use CMake to configure and compile the code

cd $FLEXI_DIR
mkdir build; cd build
cmake ../
make

The executable flexi is now contained in the FLEXI directory in build/bin/. Custom configurations of the compiler options, dependencies and code features can be set using

ccmake ../

Running the code

Navigate to the directory of the tutorial cavity and run FLEXI

cd $FLEXI_DIR/tutorials/cavity
$FLEXI_DIR/build/bin/flexi parameter_flexi.ini

Used libraries

FLEXI uses several external libraries as well as auxiliary functions from open source projects, including:

ligaohua/flexi-hybrid