Running-FELiCS#

Welcome to Running-FELiCS!

FELiCS uses four types of files:

.json - configuration files
.msh - mesh files
.fel - data files for input mean flow files and solution files
.xdmf - metadata files referencing the solution files for display in Paraview

Overview#

Below is an overview chart illustrating the workflow in FELiCS. It shows what input files are necessary, and the different outputs. Each component is linked to relevant documentation and tutorials to help guide you through the process.

        flowchart LR
    subgraph Input["Input Data"]
        A[Mean or Base<br>Flow Data<br> <a href="../Tutorials/cylinder_wake.html">see Tutorial 1</a>]
        click A "../Tutorials/cylinder_wake.html" _blank
        style Input fill:#f1faee,stroke:#457b9d,stroke-width:2px
        style A fill:#cdb4db,stroke:#333,stroke-width:1px
    end

    subgraph PrepFiles["Case Files"]
        B1[settings.json<br><a href="./FELiCS_settings.html">see details</a>]
        B2[.fel file<br><a href="./fel_file.html">see details</a>]
        B3[.msh file<br><a href="../Tutorials/cylinder_wake.html">see Tutorial 1</a>]
        B4[boundaries.json<br><a href="./FELiCS_settings.html">see details</a><br><a href="../Tutorials/modal_analysis.html">see Tutorial 2</a>]
        B5[mixture.json<br><a href="./FELiCS_settings.html">see details</a>]

        style PrepFiles fill:#f1faee,stroke:#457b9d,stroke-width:2px
        style B1 fill:#ffafcc,stroke:#333,stroke-width:1px
        style B2 fill:#ffafcc,stroke:#333,stroke-width:1px
        style B3 fill:#ffafcc,stroke:#333,stroke-width:1px
        style B4 fill:#ffafcc,stroke:#333,stroke-width:1px
        style B5 fill:#ffafcc,stroke:#333,stroke-width:1px


    end

    C[FELiCS<br><a href="./FELiCS_commands.html">see details</a>]
    style C fill:#e76f51

    subgraph Output["Output"]
        D1[Modal Analysis<br><a href="../Tutorials/modal_analysis.html">see Tutorial 2</a>]
        D2[Resolvent Analysis<br><a href="../Tutorials/Resolvent_Analysis.html">see Tutorial 3</a>]
        D3[Input-Output<br>Analysis<br><a href="../Tutorials/input_output_analysis.html">see Tutorial 4</a>]
        style Output fill:#f1faee,stroke:#457b9d,stroke-width:2px
        style D1 fill:#a8dadc,stroke:#333,stroke-width:1px
        style D2 fill:#a8dadc,stroke:#333,stroke-width:1px
        style D3 fill:#a8dadc,stroke:#333,stroke-width:1px


    end

    A ==> B2
    B1 ==> C


    B2 & B3 & B4 & B5 -. path .-> B1

    C ==> D1
    C ==> D2
    C ==> D3

    linkStyle default stroke:#8e8d8f,stroke-width:2px

The typical running folder contains:

.
├ mesh.msh
├ meanflow.fel
├ settings.json
├ boundaries.json
├ mixture.json
└── output_dir

where

mesh.msh - Mesh file generated by the user with Gmsh (in Version 2 ASCII format).
meanflow.fel - Contains the mean flow fields required for the set of equations being solved and the coordinates of points where the mean flow is known. The .fel extension is used to single out FELiCS meanflow files but these files use classic hierarchical data formats (e.g. .h5).
settings.json, boundaries.json, mixture.json - Configuration files needed to run.
output_dir - Output directory, must correspond to the Case{ExportFolder} field in the settings.json file.

Mesh file#

Your mesh file needs the format .msh. This can be generated for instance with GMSH. Make sure the .msh file is saved in Version 2 ASCII. An example for the mesh generation is provided in Tutorial 2.

Mean flow file#

The base flow can be obtained from numerical simulations, experimental results or analytical models. A RANS mean field can also be computed using the finite element Newton solver FlowSolver.py integrateed in FELiCS. The relevant mean flow information (velocities, pressure, viscosity, forcing and response domains, …) are encapsulated in a .fel file. The construction of such a file is presented in fel file in FELiCS.

Configuration files#

All the input parameters are loaded from the following .json files:

settings.json: contains the analysis settings.
boundaries.json: contains the boundary conditions.

The contents of the configuration files are detailed here.

Calling FELiCS#

To start a computation with FELiCS, use the commands detailed here

Outputs#

After running an analysis the output directory will contain the following file types:

.
└── output_dir
    ├── solution.h5
    ├── solution.xmf
    ├── MeanFlow.h5
    ├── MeanFlow.xmf
    ├── mesh.h5
    ├── spectrum.csv
    └── log
        ├── felics_29.11.2025-10.44.56.log
        └── felics_29.11.2025-10.45.01.log