Palabos

The Palabos library is a framework for general-purpose computational fluid dynamics (CFD), with a kernel based on the lattice Boltzmann (LB) method.
It is used both as a research and an engineering tool: its programming interface is straightforward and makes it possible to set up fluid flow simulations with relative ease, or, if you are knowledgeable of the lattice Boltzmann method, to extend the library with your own models.
The original programmer interface of the library is written in C++. It has practically no external dependencies and is therefore extremely easy to deploy on various platforms, including parallel systems like the BlueGene.
Additional programmer intefaces are available for the Python and Java programming languages, which make it easier to rapidly prototype and develop CFD applications. There exists currently no graphical user interface; some amount of programming is therefore necessary in order to get an application running.
Especially with the Python scripting interface, the developed code can however be pretty informal, and easy to produce with help of the provided examples.