FEST-3D vs Step

FEST-3D is a Fortran 90 finite-volume computational fluid dynamics solver for Navier–Stokes flow problems on structured grids, developed for aerodynamics. It handles incompressible and compressible flows, including inviscid, laminar, transitional and turbulent cases. Users can select among flux schemes, reconstruction methods, time-integration options, turbulence models and transition models. MPI distributes computations across processors on one or more machines. The solver is free and open source under the GNU General Public License version 3.0, with source available from GitHub. Its installation script supports Ubuntu/Debian, CentOS and macOS, while manual installation instructions cover Linux. Building requires a Fortran compiler, an MPI library, CMake and Make. Tutorials in a separate repository address verification cases such as a smooth bump, lid-driven cavity, flat plates and an airfoil. FEST-3D writes VTK or Tecplot output for separate visualization tools. Grid generation and post-processing are outside the solver, and the project notes its halt/stop condition does not work with MPI.

Step is a free Linux desktop application for exploring physical systems through interactive simulations. Users can change body and force properties while a simulation runs. Supported models include two-dimensional classical mechanics, molecular dynamics, sound waves, and deformable bodies, with particles, damped springs, gravitational and Coulomb forces, rigid bodies, and collision handling. Step calculates unit conversions, expressions, error propagation, and solver error estimates. Explicit and implicit solvers reach 8th order, with optional adaptive timesteps; most require GSL. Graph, meter, and tracer tools visualize results, while a controller changes properties using keyboard shortcuts. Tutorials, example experiments, object information, and an integrated Wikipedia browser provide learning material. More examples can be downloaded through KNewStuff. Expression calculations such as unit conversion require libqalculate. Step is GPL-2.0+ software, and its StepCore library can be used separately. The listed release is Step 26.08.2, released 2026-10-08.