FeenoX is a computational tool that can solve engineering problems which are usually casted as differential-algebraic equations (DAEs) or partial differential equations (PDEs). It is to finite elements programs and libraries what Markdown is to Word and TeX, respectively. In particular, it can solve dynamical systems defined by a set of user-provided DAEs (such as plant control dynamics for example)
mechanical elasticity
heat conduction
structural modal analysis
neutron diffusion
neutron transport
FeenoX reads a plain-text input file which contains the problem definition and writes 100%-user defined results in ASCII (through PRINT or other user-defined output instructions within the input file). For PDE problems, it needs a reference to at least one Gmsh mesh file for the discretization of the domain. It can write post-processing views in either .msh or .vtk formats.
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Recent Releases
1.107 Jul 2025 18:45
minor bugfix:
Misc for Debian packaging.
Steady-state writer in VTU `.vtu` format.
Skip some tests in big-endian architectures.
`READ_MESH` can read CalculiX's `.frd` output files.
`utils/fee2ccx` converter from FeenoX's `.fee` to CalculiX's `.fee`.
Links to examples and tests in HTML manual.
Cleanups to create `debian` directory in Salsa (see ).
Distribution binaries are dynamic instead of static.
`BC` type `adiabatic` in `thermal`.
`TIME_PATH` with PETSc and SUNDIALS.
Improved vector initialization syntax.
Remove compilation date to allow reproducible builds.
BCs as arrays instead of linked lists.
Option `--ast`.
`BC GROUPS` to select many labels at once.
Cleanups to create Debian `dsc`.
Use `config.h` instead of `version.h`.
Compute perimeters using second-order precision.
Bump GSL to v2.8.
`INTEGRATE` expressions of `nx`, `ny` and `nz`.
Create `_cog` variables for points as well.
For evaluation of derivatives at arbitrary locations.
Paper in FOSS: .
1.017 Dec 2024 17:55
major feature:
option --check
README for engineers, hackers and academics
thermal tutorial
thermal radiation tests
two-dimensional quasi-random number sequences
non-zero Neumann BCs in neutron diffusion
LABEL in now an alias for PHYSICAL_GROUP in MATERIAL
explicit fission spectrum
EIGEN_DIRICHLET_ZERO keyword
special variable mumps_ictnl_14 to control MUMPS' over-relaxation factor
improved MPI execution
verification with MMS
PRINTF and PRINTF_ALL instructions
improved memory handling when building elemental objects
PREALLOCATE and ALLOW_NEW_NONZEROS options
choose either to fail or allow missed BCs
updated internal naming of FEM matrices to match the doc
dump element drawings, node ordering and shape functions with --elements_info
cleaned up source distributions
CI using Github actions
Los Alamos criticallity benchmarks in tests
support for reading VTK v5 files
WRITE_RESULTS keyword
split examples by problem type
YAML blocks in input file for metadata are allowed (so far they are ignored by FeenoX)
0 (or 0 or (1)) expands to the base name of the main input, i.e. without the .fee extension
bracketed argumens so 1 1 (1) is a valid string
multi-group neutron transport with discrete ordinates ( S N method)
mimicked-nodes BCs
read mesh fields from VTK files
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