OpenFoam
OpenFOAM is a open source computational fluid dynamics software, this may be a bit unnecessary at this time, but i thought i would just bring it up for future reference.
Here is a link to their website:
FYI FreeCAD 0.17 has OpenFOAM capability. See https://forum.freecadweb.org/viewtopic.php?style=4&f=18&t=21576