Enable additional states / equations in onedim

[ischoegl]

Fixes # [cantera-users] Additional Equations in StFlow

Changes proposed in this pull request:

• add nSpecies() { return m_nsp; } to StFlow.h
• replace m_nsp = m_flow->nComponents() - c_offset_Y; by m_nsp = m_flow->nSpecies(); in boundaries1D.cpp

Proposed change enables decoupling of number of components from the number of species.

[codecov]

Codecov Report

Merging #624 into master will decrease coverage by <.01%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master     #624      +/-   ##
==========================================
- Coverage   68.54%   68.53%   -0.01%     
==========================================
  Files         363      363              
  Lines       39978    39978              
==========================================
- Hits        27401    27400       -1     
- Misses      12577    12578       +1

Impacted Files	Coverage Δ
src/oneD/boundaries1D.cpp	51.24% <50%> (ø)	⬆️
src/transport/GasTransport.cpp	90.77% <0%> (-0.21%)	⬇️

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[ischoegl]

Not sure about codecov flagging files that were not changed (GasTransport.cpp?). The push request is limited to 5 lines of code ...

PS: a functional (albeit rudimentary) example for code with added equations is posted on ischoegl/ctapp (object NewFlow defined in C++)

[speth]

I can see how the change in Inlet1D is necessary to be able to add state variables, but I'm kind of surprised that this is sufficient. Certainly, there's a lot more work to be done to make the 1D solver more generically extensible, but this seems fine for what it does.

The coverage failures are confusing but not a problem. The test suite passing is what's important.

[speth]

Instead of introducing a new method here, you could just access the number of species from Inlet1D as m_flow->phase().nSpecies().

[ischoegl]

Yes, the simplicity of the fix surprised me also. Thanks for the suggestion: I didn't think of calling m_flow->phase(); I created the new method as neither m_thermo nor m_nsp were accessible.

I'll report back.

[ischoegl]

@speth per your suggestion I eliminated the StFLow::nSpecies() method I had added, now accessing m_flow->phase().nSpecies() instead. The code compiles and the test suite passes.