Hi,

Can I only define derivaties of time? Is it not possible to implicitly state dy / dx, for instance?

Regards,
Pingen

Hi,

Not yet.
There is some discussion in the Modelica Association
about adding them to the language but they will maybe
come in Modelica 4 or 5. We are now at Modelica 3.0.

Quote from Modelica Specification 3.0:
"Basically, all Modelica language elements are mapped to differential, algebraic and discrete equations.
There are no language elements to describe directly partial differential equations, although some types
of discretized partial differential equations can be reasonably defined, e.g., based on the finite volume
method and there are Modelica libraries to import results of finite-element programs."
See here more: http://www.modelica.org/documents/ModelicaSpec30.pdf

Cheers,
Adrian Pop/

Yes, it is not possible with standard Modelica. You need to write numerical routines on your own to handle PDE´s.