If you want to try modelling some stuff with petri nets, or rather more advanced abstractions, there's the FLOSS tool called "Renew" (Reference Net Workshop) fr

If you want to try modelling some stuff with petri nets, or rather more advanced abstractions, there's the FLOSS tool called "Renew" (Reference Net Workshop) from the university of Hamburg. The UX could be better but it's an interesting tool. It uses reference nets (which are more powerful than petri nets because you can have subnets and modularize your simulations quite nicely). It's in Java and you can execute Java-code from the models (if a transaction fires) which is pretty interesting. The last update to the site was in 2016 but the tool is stable and can be used. They also have a nice User Guide as PDF on the site: http://www.renew.de/ http://www.renew.de/