OpenFOAM is described as 'The leading free, open source software for CFD, owned by the OpenFOAM Foundation and distributed exclusively under the General Public Licence (GPL). The GPL gives users the freedom to modify and redistribute the software and a guarantee of continued free use, within' and is an app. There are more than 10 alternatives to OpenFOAM for Windows, Linux, Mac and MATLAB. The best OpenFOAM alternative is SimFlow. It's not free, so if you're looking for a free alternative, you could try FEATool Multiphysics or Elmer. Other great apps like OpenFOAM are COMSOL Multiphysics, ANSYS Fluent, KRATOS Multiphysics and Code_Aster.