Tutorial fluid modelling

[vlipovac]

Closes #1254

Proposed changes

Adding a tutorial for modeling of multiphase and multicomponent fluids.

Changing the configuration of phases to omit the default EquationOfState and hence simplifying the setup for models not relying on EoS computations.

Types of changes

• Minor change (e.g., dependency bumps, broken links).
• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• Testing (contribution related to testing of existing or new functionality).
• Documentation (contribution related to adding, improving, or fixing documentation).
• Maintenance (e.g., improve logic and performance, remove obsolete code).
• Other: Tutorial

Checklist

• The documentation is up-to-date.
• Static typing is included in the update.
• This PR does not duplicate existing functionality.
• The update is covered by the test suite (including tests added in the PR).
• If new skipped tests have been introduced in this PR, pytest was run with the --run-skipped flag.

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[mariusnevland]

Some high-level comments after the first readthrough:

• As a complete newbie to multiphase, multicomponent flow, I do not know e.g. the difference between overall fractions and partial fractions, as well as some other technical terms. Maybe it is a good idea to state some "prerequisites" for the tutorial?

• It is unclear to me how to use the heuristic approach in the case of multiple phases and/or components. Did I understand correctly that the default constitutive laws will stop working if I add more phases/components? If so, how can they be redefined?

• Regarding the EoS classes, I do not understand how the return_dummy_properties() function should look like in the case of non-trivial phase properties. But otherwise, this code block was very helpful in understanding how to use the EoS framework.

• It would be very nice to have an actual runable model in the very end, but would this significantly increase the complexity of the tutorial? Is it possible to construct some "minimal working example" that still introduces most/all of the important functionality, e.g. some relatively simple two-phase, two-component setup?

[keileg]

Thanks for the feedback @mariusnevland. I'll have a look and keep your comments in mind.

[keileg]

Most important: This will become extremely useful for everyone as we introduce more advanced fluid modeling.

I only managed to read half the tutorial before I had to run, will try to cover the second half no later than Monday. I tried to keep the comments on a high level, it seems to me we should focus on getting the context and general disposition of the tutorial right before getting into details.

[keileg]

I left a few more comments. @vlipovac I suggest we discuss how to approach this PR at some point.

[vlipovac]

Some high-level comments after the first readthrough:

• As a complete newbie to multiphase, multicomponent flow, I do not know e.g. the difference between overall fractions and partial fractions, as well as some other technical terms. Maybe it is a good idea to state some "prerequisites" for the tutorial?
• It is unclear to me how to use the heuristic approach in the case of multiple phases and/or components. Did I understand correctly that the default constitutive laws will stop working if I add more phases/components? If so, how can they be redefined?
• Regarding the EoS classes, I do not understand how the return_dummy_properties() function should look like in the case of non-trivial phase properties. But otherwise, this code block was very helpful in understanding how to use the EoS framework.
• It would be very nice to have an actual runable model in the very end, but would this significantly increase the complexity of the tutorial? Is it possible to construct some "minimal working example" that still introduces most/all of the important functionality, e.g. some relatively simple two-phase, two-component setup?

@mariusnevland

1. I have added some links in the tutorial to the implementation of various fractions. The docstring take care of the formal definition.
2. There are a couple of notes after the implementation of FluiDensityFromPressure is discussed, They cover your concerns. It does not stop working, but all phases get the same properties assigned. for more phases, you need to define more functions inside the factory method, and then return the right one depending on the argument phase. Please have a look again and let me know if it is still not clear.
3. The return dummy is just a placeholder to return some values so that prepare_simulation() can be called. In essence you just have to return a filled PhaseProperties instance with all the values from your computation.
4. Yes it would, it's not a trivial task to set a thermodynamic model for multiphase flow. I am not sure we want to have that as part of a tutorial, if there is nothing in the source code (so far).