Modelica é uma boa ferramenta para a simulação e modelagem.

That it has a free version and do what it says. Can be used for simple and complex problems and it easy for amateurs as its learning curve is really fast. From a modeling point of view, block creation and equation formulation things are quite straightforward. The capability of library creation is very important and well used. Modelica as a modeling language is powerful and easy to use.

Eu achei bastante bom em representar propriedades físicas.