If you use the Modelica Language for simulation it's basically a rite of passage to at least try out OpenModelica, although your mileage on various operating systems and versions thereof can vary wildly (you can always ask for the money back that you didn't pay).
NEWS: SysML Extension for Physical Interaction and Signal Flow Simulation (SysPhS): New technology assessment trail: TRAIL: SysPhS-1.1 specification body figures in MagicDraw SysML (or Cameo Systems Modeler) vs Modelica
NEWS: SysML Extension for Physical Interaction and Signal Flow Simulation (SysPhS): New technology assessme
Dedicated to chromæsthesia, the PLAY logo created with PureData/GEM sound and visuals synthesis can be both seen and heard simultaneously.
Pure Data (or just Pd) is an open source visual programming language for multimedia.