Consider a block describing a channel with two opposite walls.
Currently in order to grade the mesh towards the walls and have a
uniform region in the centre the channel would need to be spit into 3
blocks. With the new multi/sectional grading this can be achieved in a
single block e.g.
blocks
(
hex (0 1 2 3 4 5 6 7) (20 60 20)
simpleGrading
(
1
((0.2 0.3 4) (0.6 0.4 1) (0.2 0.3 0.25))
1
)
);
In this example the block is divided uniformly in the x and z -directions
and split into three grading sections in the y-direction described by
three triples: ((0.2 0.3 4) (0.6 0.4 1) (0.2 0.3 0.25)). Each of the
grading sections is described by a triple consisting of the fraction of
the block, the fraction of the divisions and the grading ratio (size of
first division/size of last division). Both the fraction of the block
and the fraction of the divisions are normalized automatically so they
can be specified scaled in anyway, e.g. as percentages:
blocks
(
hex (0 1 2 3 4 5 6 7) (20 60 20)
simpleGrading
(
1
((2 3 4) (6 4 1) (2 3 0.25))
1
)
);
and they need not sum to 1 or 100.
This is very new functionality and not well tested but backward
compatibility has been well tested so all existing blockMeshDicts should
parse correctly.
in particular to pick-up the DebugSwitches from system/controlDict at
global construction time.
Disadvantage is that system/controlDict is only picked-up if the
OpenFOAM application is executed IN the case directory. The directory
provided by the -case option is not yet known as the arguments have not
yet been parsed.
Furst, J. (2013).
Numerical simulation of transitional flows with laminar kinetic energy.
Engineering MECHANICS, 20(5), 379-388.
Thanks to Jan-Niklas Klatt for analysing problems with and correcting
the implementation and testing corrections to the model proposed by
Furst.
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
