OpenFOAM vs RELAP5-3D

OpenFOAM is a free, open-source computational fluid dynamics toolbox for simulating fluid flow, heat transfer, and related physical processes. It provides pre-processing, mesh generation, solvers for different flow and physics problems, and post-processing tools. Built-in utilities include blockMesh and snappyHexMesh, and it can convert meshes from external formats. ParaView visualization is supported through the paraFoam launcher, reader modules, VTK conversion, and VTK output during simulations. OpenFOAM runs on Linux, macOS, and Windows, and supports self-hosted use. Its current release is v2606, released on 26 June 2026; GPU offloading is available as a compile-time option, with that work on a separate development track. It is distributed under the GNU General Public Licence. OpenCFD offers a one-year support package for installation, fixes, updates, CFD assistance, and code customization, subject to a yearly service-hours maximum. It does not respond to support queries without a prior package. Training courses are also offered, with prices provided through a schedule or enquiry process.

RELAP5-3D has no write-up on Specifiction yet; its figures are above.