Add Multicomponent Sips isotherm.

[ronald-jaepel]

This PR continues work by @sleweke to add the multicomponent Sips isotherm to CADET-Core.

I've rebased the branch onto master and added several changes to documentation and tests.

Status and ToDos:

• Add Flux and Jacobian Implementation
• modify to follow CADET standard of 1/n for exponent in Freundlich isotherms.
• ensure stability at c_p == 0, either:
  • x copy approach of multicomponent Freundlich ( τ - a small constant that ensures numerical stability)
  • copy approach of FreundlichLDF with model approximation
• Add tests
• Complete tests
• Add documentation

Reference is Sips, R.: On the structure of a catalyst surface. J. Chem. Phys. 16, 490–495 (1948)

[ronald-jaepel]

For reference, here's the current state of the documentation:

Multi Component Sips

**Group /input/model/unit_XXX/adsorption – ADSORPTION_MODEL = MULTI_COMPONENT_SIPS**


``IS_KINETIC``
   Selects kinetic or quasi-stationary adsorption mode: 1 = kinetic, 0 =
   quasi-stationary. If a single value is given, the mode is set for all
   bound states. Otherwise, the adsorption mode is set for each bound
   state separately.

===================  =========================  =========================================
**Type:** int        **Range:** {0,1}  		    **Length:** 1/NTOTALBND
===================  =========================  =========================================

``SIPS_KA``
   Adsorption rate constants

**Unit:** :math:`s^{-1}`

===================  =========================  =========================================
**Type:** double     **Range:** :math:`\ge 0`   **Length:** NCOMP
===================  =========================  =========================================

``SIPS_KD``
   Desorption rate constants

**Unit:** :math:`mol~m_{SP}^{-3}~s^{-1}`

===================  =========================  ==================================
**Type:** double     **Range:** :math:`\ge 0`   **Length:** NCOMP
===================  =========================  ================================== 

``SIPS_QMAX``
   Maximum adsorption capacities

**Unit:** :math:`mol~m_{SP}^{-3}`

===================  =========================  ==================================
**Type:** double     **Range:** :math:`\gt 0`   **Length:** NCOMP
===================  =========================  ================================== 

``SIPS_EXP``
   Freundlich-type exponent

===================  =========================  ==================================
**Type:** double     **Range:** :math:`\gt 0`   **Length:** NCOMP
===================  =========================  ================================== 

``SIPS_REFC0``
   Reference liquid phase concentration (optional, defaults to
   :math:`1.0`)


**Unit:** :math:`mol~m_{MP}^{-3}`

===================  =========================  =========================================
**Type:** double     **Range:** :math:`\gt 0`   **Length:** 1
===================  =========================  =========================================

``SIPS_REFQ``
   Reference solid phase concentration (optional, defaults to
   :math:`1.0`)


**Unit:** :math:`mol~m_{SP}^{-3}`

===================  =========================  =========================================
**Type:** double     **Range:** :math:`\gt 0`   **Length:** 1
===================  =========================  =========================================

``SIPS_LINEAR_THRESHOLD``
   Threshold for linearization. Originally, the liquid phase concentration
   enters the adsorption rate via a power term. Below this threshold, a
   quadratic approximation is used instead. This ensures numerical stability.

**Unit:** :math:`mol~m_{MP}^{-3}`

===================  =========================  =========================================
**Type:** double     **Range:** :math:`\gt 0`   **Length:** 1
===================  =========================  =========================================

[jbreue16]

wait a minute why is the CI failing when ive only updated the copyright.. ive seen this before ..

[ronald-jaepel]

That's unrelated. It's because of my error with the commit I've accidentally made to master, that is now #358

edit: No, nevermind, it's not. But it also happens on that other PR.

edit2: Yes, it might be, because the line in the log that throws the error is the one I changed. Will report back with more detail.

edit3: Yes, it was unrelated due to the changes in #358 . After re-running the CI it now completes fine.

[jbreue16]

I think we should keep a separate commit for changes in the freundlich isotherm and squash the rest into another commit?

[ronald-jaepel]

I'll keep the commit by Sam as-is to retain authorship, squash all Sips made by me into one and all Freundlich by me into one.

[jbreue16]

You can also squash them all into Sams, then add yourself as co author by adding the following to the commit description:
Co-authored-by: Ronald Jäpel

[ronald-jaepel]

Is squashed. Ready to merge