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modelicadymola

Define Model Parameter as Variable

I am attempting to define the parameter of a model (block) as a variable. For example:

Real WallThickness = 0.5;
Real WallConductance = 10*WallThickness;
Modelica.Thermal.HeatTransfer.Components.ThermalConductor TopPanelConductor(G=WallConductance);

I would like to define "G" so that it remains constant throughout the simulation but the coefficient is updated prior to the simulation based on the other variable "WallThickness". When defining the ThermalConductor parameter "G" as a variable in the model, which is being calculated elsewhere, I get the error message: 

The variability of the definition equation:
TopPanelConductor.G = WallConductance;
is higher than the declared variability of the variables.

I would like to define the parameters of a model as a variable. This allows me to create parametric definitions as the geometry of the all changes. Is there a way I can make this definition work?

Solution

  • You mean the geometry changes during simulation? If so, you'll have to rewrite the ThermalConductor model to work with a variable G, because a variable cannot be assigned to a parameter. A variable may vary during the course of simulation. A parameter is fixed at the start of simulation, but can be changed from run to run without recompiling the model, which allows for quicker iteration/design work.

    Note that you can also calculate a parameter from other parameters that you define, e.g. to calculate a heat transfer coefficient from a given wall thickness (which you vary from simulation run to simulation run).