Dynamics TODO list

[dallan-keylogic]

There are many outstanding issues with dynamic or multiperiod models that need to be resolved. They will be aggregated in this issue. This list is incomplete; you can help by expanding it.

• Standardize behavior of initialization routines when more than one time point is present
• Revisit process_base.fix_initial_conditions and roll out standardized methods to provide initial conditions for dynamic models by loading in a .json file as well as solving a steady-state problem at t0.
• Reevaluate whether every model that allows dynamic=True should allow it, or whether it should be retired (Heater, I'm looking at you).
• Add documentation explaining the concepts of setting has_holdup=True and dynamic=True in a model
• Add example where we take a simple unit model (maybe a CSTR?) and make it dynamic.
• Add a method to return the dynamic block sent to PETSc in the same way that Add function to PETSc interface to return initial condition problem #1443 returns the steady-state problem block
• Add a diagnostic method to see if variables at, say t=t1 appear in (non-discretization) equations at t=t2.
• Can we add a diagnostic method to check if a DAE has index greater than 1?

[andrewlee94]

A few more thoughts for inclusion (I suggest those with more experience think about these and add any important ones above):

1. Support normalized time domains - this could just be a new config argument to flowsheet block, which adds a scaling factor that can be picked up by control volumes.
2. Look at standardizing multiperiod models, as different projects seem to have implemented their own approaches. Notably, FlowsheetBlock already supports multiperiod models by setting dynamic=False and providing a time_set argument (effectively creating steady state models at each time element).

[Robbybp]

Revisit process_base.fix_initial_conditions and roll out standardized methods to provide initial conditions for dynamic models by loading in a .json file as well as solving a steady-state problem at t0.

I have written some tools that may be useful for this, e.g. this example. See lines 54-55, where I load data from a steady state model into plant and controller models for initialization. The data could also come from a dynamic model or a json file.