Go here for Woo documentation.

Woo is a flexible and extensible open-source code used for (mostly) Discrete Element (DEM) simulations. It is geared towards non-trivial, challenging scenarios − sieving, segregation, conveyors, membranes and others. It is also a solid framework for developing new types of simulations, offering non-trivial services such as tight C++/Python integration, data persistence, GUI inspection, visualization contexts, parallelism, batch running, portability.

The computational core is written in c++ (plus Python scriptability) and provides many DEM algorithms, integrated visualization & reporting facilities, outputs suitable for external tools (e.g. Paraview), batch simulations; supports Linux (primary platform) and 64bit Windows. As open-source, it may be used on unrestricted number of CPUs/computers;

We, the people behind Woo can also tweak everything for you: for a negotiated price, you obtain a package customized to your problem, ready to be run by engineers without months of programming training. This package will consist of preprocessor tailored to your particular problem, plus the solver.