A variety of fluid-flow problems deal with more than one phase and OpenFOAM has a Lagrangian particle tracking library for this kind of problem.

The basic model provides tracking and coupling with the Eulerian phase, allowing for simple implementation of spray and other multi-phase modelling.

The standard OpenFOAM release includes a complete set of atomization, breakup, collision, and evaporation models.

As always, the open architecture allows users to freely add their own models.