For most people, OpenFOAM is a Computational Fluid Dynamics (CFD) package, but in fact it is a package that can actually solve any continuum mechanics problem. Admittedly, CFD is one of these, but there are others as well (e.g. magnetohydrodynamics).

Open source
OpenFOAM was released under an open source license in 2004. This started off a development that is still gaining momentum today. Many developers are extending OpenFOAM for their own needs, some are delivering their work back to the OpenFOAM user community and OpenCFD is constantly extending and enriching the software. Today, there are vast numbers of models and solvers in OpenFOAM, making it one of the most powerful packages in its field.

Advantages
One of the most striking things about OpenFOAM is the fact that it is completely free. But for many users the main advantage of OpenFOAM is that its source code is publicly available. So, if you know a bit about programming, you can inspect the code and see what it does. If the outcome of your simulation is not what you expected, you can find out the cause. And: if you want additional functionality, you can create it yourself. Or you can let someone else build it for you.

Disadvantage
Of course, there are not only advantages. The main disadvantage is probably that OpenFOAM requires you to do a lot of configuration work yourself. But the flipside of this is that it also gives you a lot of control over the configuration. This allows you to run models for which the commercial packages just don’t offer the right buttons. Also, there are several ways in which you can get support for OpenFOAM.