Effect of the pipe diameter in speed of the simulation - Modelica

Question

I modeled a hydraulic system in Modelica which can be simulated in certain conditions, e.g. when the diameter of the pipe, which is located before the "Auslass" boundary condition, is 5 mm, when I change it to 8 mm, simulation doesn′t proceed. It slows down the progress of the simulation considerably. What can be reason of the difference in speed of the simulation only if the diameter of the pipe is changed? I added the link of the block diagram of the model.

Best regards

Answer 1

This can be a number of things. From a screenshot it is only possible to give very general advice. As it is "only" a parameter the system's structure shouldn't change. Therefore it is likely related to dynamics of the system. I would take a look at the solver log first, starting with the number of computed steps or the step-size. If that changed in an order of magnitude of the slow-down you experience this is a good starting point.

Another issue could be chattering, which could be judged with knowledge about the number of events that happened. These should also be visible from the solver log.

Some additional information that would help:

• Which Modelica-Tool are you using?
• The model itself (with which all of the below can be generated)
• The solver log (before and after the parameter change)
• The translation log incl. system properties like the sizes of equation systems (before and after the parameter change)

I'm afraid without any additional information you will not get utterly helpful advice...