OpenModelica zone

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).
2021-01-11 OpenModelica no longer has DMG install bundles for Mac, and currently does NOT install on Mac Big Sur using MacPorts!

If you can do the work you wish with OpenModelica, by all means stick with

Modelica zone

From the Modelica Association home page:
The Modelica Language is a non-proprietary, object-oriented, equation based language to conveniently model complex physical systems containing, e.g., mechanical, electrical, electronic, hydraulic, thermal, control, electric power or process-oriented subcomponents.

Modelica uses a text based modeling language behind the scenes that is primarily intended for use with "patch-based" graphical wiring up of components.