You're out of luck.

From Peter Fritzson's book (8.5 Partial Differential Equations):
This section describes a generalized in operator that at the time of this writing is not yet formally accepted in the Modelica language specification

From the Modelica 3.2 specification (Preface):
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.

hello
is it possible to model Differential Equations in OpenModelica? I mean without dealing with partial concepts.

Here is an example on how to solve the heat transfer equation in OMNotebook. Is it possible to reduce the simulation time with some sort of simulation options?

function array2time 
  //this function gets an array of data and the time
  //it returns a time dependend stepwise result
  //each array value corresponds to a specific time interval
  input Real array[:];
  input Real time;
  output Real result;
protected
Integer array_length;
Real delta_time;
Real stop_time;
algorithm
stop_time:= 1;
array_length := size(array,1); //number of values
delta_time:=stop_time/(array_length-1); //size of time interval
for k in 1:array_length loop
  if time >delta_time*(k-1)-delta_time/2 and time <= delta_time*k-delta_time/2 then
   result:=array[k];
  end if;
end for; 
  //if time >=stop_time-delta_time/2 then
  // result:=array[array_length-1];
  //end if; 
end array2time;

loadModel(Modelica);

model HeatTransfer "One Dimensional Heat Transfer"
import Modelica.SIunits;

//Configuration parameters
parameter Integer n=100 "Number of Nodes";
parameter SIunits.Density rho=1 "Material Density";
parameter SIunits.HeatCapacity c_p = 1;
parameter SIunits.ThermalConductivity k=1;
parameter SIunits.Length L=10 "Domain Length";

//Temperature Array
SIunits.Temp_K T_array[n] (start=fill(300,n)) "Nodal Temperatures";
//variabes
Real x_array[n];
Real x;
Real T;   
protected

// Computed parameters
parameter SIunits.Length dx=L/n "Distance between nodes";
equation

// Loop over interior nodes
for i in 2:n-1 loop
x_array[i] = i*dx;
rho*c_p*der(T_array[i]) = k*(T_array[i+1]-2*T_array[i]+T_array[i-1])/dx^2;   
end for;

// Boundary Conditions
x_array[1] = 0;
x_array[n] = L;
 
T_array[1] = 1000;
T_array[n] = 300;

//array2time
x = array2time(x_array,time);
T = array2time(T_array,time);
end HeatTransfer;


simulate(HeatTransfer, method = "dassl", numberOfIntervals=100)


plotParametric(x,T)

Here is another thread on PDEs in this forum: https://www.openmodelica.org/index.php/ … pic?id=147

Hi everybody,

I made this GitHub repository to collect all the materials i could find the internet regarding solving partial differential equations in Modelica. please join me to push this matter a little bit forward:
https://github.com/Foadsf/ModelicaPDE

Hello guys,

Thank you for your help in advance.

I am new to Modelica and i am using Dymola Software.
I have a thermal power plant model that was built by another person and I am trying to extract the differential equations or the state space representation of this model.

I translated the model to FMU file and exported it to Simulink. The model worked fine and gave proper simulation but it is treated as a black box with some inputs and outputs only and i cannot read the state variables of the system.

i got the dsmodel.mof file but it is not possible to read the ODE from there since it is a very complex system and i cannot extract the right equations. 

Does anyone know how to get a clear representation of the differential equations of the model in Dymola ?

Firas