Tips & Tricks: How to decrease model stiffness in Simscape ?

Hi Community!

A little bit of context: I am currently struggling to run a Simscape model of a steam engine using the 2-Phase fluids library. It includes valves and translational mechanical converters, etc.

It is very dependent on the solver used and its parameters, and the model's parameters. Sometimes it will run without any issue, sometime it will crash after couple of milliseconds...

Running the Simscape Solver Profiler shows that I have high stiffness (Eigenvalue around -1e+6), which is most likely the reason why I have these fails.

I am not really planning on sharing the model for now but more asking for tips and tricks to reduce/decrease a Simscape model stiffness.

I tried these tricks that usually worked in the past but did not help in the aforementioned case:

• Add flow resistance between components to "decouple" states variables;
• Add some "inertia" to the model between components (constant volumes, pipes, ...) to slow down the dynamics;

These tricks are more on having a solver capable of computing stiff system:

• Use a implicit solver;
• Use variable time step solver;

Do you have any other tips and tricks? Or any idea what could causes such high stiffness in a Simscape model?

And yes I read these:

https://www.mathworks.com/help/simscape/ug/reduce-numerical-stiffness.html

https://www.mathworks.com/help/simscape/ug/simscape-stiffness-analysis.html

Thanks!