Community contribution from Johan Roenby, DHI

IsoAdvector is a geometric Volume-of-Fluid method for advection of a
sharp interface between two incompressible fluids. It works on both
structured and unstructured meshes with no requirements on cell shapes.
IsoAdvector is as an alternative choice for the interface compression
treatment with the MULES limiter implemented in the interFoam family
of solvers.

The isoAdvector concept and code was developed at DHI and was funded
by a Sapere Aude postdoc grant to Johan Roenby from The Danish Council
for Independent Research | Technology and Production Sciences (Grant-ID:
DFF - 1337-00118B - FTP).
Co-funding is also provided by the GTS grant to DHI from the Danish
Agency for Science, Technology and Innovation.

The ideas behind and performance of the isoAdvector scheme is
documented in:

    Roenby J, Bredmose H, Jasak H. 2016 A computational method for sharp
    interface  advection. R. Soc. open sci. 3: 160405.
    [http://dx.doi.org/10.1098/rsos.160405](http://dx.doi.org/10.1098/rsos.160405)

Videos showing isoAdvector's performance with a number of standard
test cases can be found in this youtube channel:

    https://www.youtube.com/channel/UCt6Idpv4C8TTgz1iUX0prAA

Project contributors:

* Johan Roenby <jro@dhigroup.com> (Inventor and main developer)
* Hrvoje Jasak <hrvoje.jasak@fsb.hr> (Consistent treatment of
  boundary faces including processor boundaries, parallelisation,
  code clean up
* Henrik Bredmose <hbre@dtu.dk> (Assisted in the conceptual
  development)
* Vuko Vukcevic <vuko.vukcevic@fsb.hr> (Code review, profiling,
  porting to foam-extend, bug fixing, testing)
* Tomislav Maric <tomislav@sourceflux.de> (Source file
  rearrangement)
* Andy Heather <a.heather@opencfd.co.uk> (Integration into OpenFOAM
  for v1706 release)

See the integration repository below to see the full set of changes
implemented for release into OpenFOAM v1706

    https://develop.openfoam.com/Community/Integration-isoAdvector

Now the interFoam and compressibleInterFoam families of solvers use the same
alphaEqn formulation and supporting all of the MULES options without
code-duplication.

The semi-implicit MULES support allows running with significantly larger
time-steps but this does reduce the interface sharpness.

fvOptions are transferred to the database on construction using
fv::options::New which returns a reference.  The same function can be
use for construction and lookup so that fvOptions are now entirely
demand-driven.

The abstract base-classes for fvOptions now reside in the finiteVolume
library simplifying compilation and linkage.  The concrete
implementations of fvOptions are still in the single monolithic
fvOptions library but in the future this will be separated into smaller
libraries based on application area which may be linked at run-time in
the same manner as functionObjects.

The old separate incompressible and compressible libraries have been removed.

Most of the commonly used RANS and LES models have been upgraded to the
new framework but there are a few missing which will be added over the
next few days, in particular the realizable k-epsilon model.  Some of
the less common incompressible RANS models have been introduced into the
new library instantiated for incompressible flow only.  If they prove to
be generally useful they can be templated for compressible and
multiphase application.

The Spalart-Allmaras DDES and IDDES models have been thoroughly
debugged, removing serious errors concerning the use of S rather than
Omega.

The compressible instances of the models have been augmented by a simple
backward-compatible eddyDiffusivity model for thermal transport based on
alphat and alphaEff.  This will be replaced with a separate run-time
selectable thermal transport model framework in a few weeks.

For simplicity and ease of maintenance and further development the
turbulent transport and wall modeling is based on nut/nuEff rather than
mut/muEff for compressible models so that all forms of turbulence models
can use the same wall-functions and other BCs.

All turbulence model selection made in the constant/turbulenceProperties
dictionary with RAS and LES as sub-dictionaries rather than in separate
files which added huge complexity for multiphase.

All tutorials have been updated so study the changes and update your own
cases by comparison with similar cases provided.

Sorry for the inconvenience in the break in backward-compatibility but
this update to the turbulence modeling is an essential step in the
future of OpenFOAM to allow more models to be added and maintained for a
wider range of cases and physics.  Over the next weeks and months more
turbulence models will be added of single and multiphase flow, more
additional sub-models and further development and testing of existing
models.  I hope this brings benefits to all OpenFOAM users.

Henry G. Weller

Improve code reuse
Add multiphaseInterDyMFoam
Retire MRFinterFoam -> now handled by interFoam with fvOptions
Update tutorials

Multiphase: Update all solvers to accommodate the split between twoPhaseMixture and incompressibleTwoPhaseMixture