The new optional entry alphap is the as phase fraction below which bubble
generated turbulence is included. The default is 1 for backward compatibility.
The purpose of this limiter is to avoid spurious turbulence generation at and
around the interface where bubbles are not present.
If the functionObject requires an object list rather than a field list the
non-named arguments are now inserted into the object list, for example
functions
{
#includeFunc writeObjects(kEpsilon:G)
}
which is equivalent to
functions
{
#includeFunc writeObjects(objects = (kEpsilon:G))
}
For example the generation term in the k-epsilon turbulence kEpsilon:G is a
temporary field that is specifically named and registered so that it can be
looked-up be the wall-function boundary conditions and requires slightly
different handling compared to normal temporary fields which are not registered.
The tutorials/incompressible/simpleFoam/pitzDaily case now demostrates this
functionality with the addition of
cacheTemporaryObjects
(
kEpsilon:G
);
functions
{
#includeFunc writeObjects(objects = (kEpsilon:G))
}
in controlDict which caches kEpsilon:G and writes it at every write time.
Description
Reciprocal polynomial equation of state for liquids and solids
\f[
1/\rho = C_0 + C_1 T + C_2 T^2 - C_3 p - C_4 p T
\f]
This polynomial for the reciprocal of the density provides a much better fit
than the equivalent polynomial for the density and has the advantage that it
support coefficient mixing to support liquid and solid mixtures in an
efficient manner.
Usage
\table
Property | Description
C | Density polynomial coefficients
\endtable
Example of the specification of the equation of state for pure water:
\verbatim
equationOfState
{
C (0.001278 -2.1055e-06 3.9689e-09 4.3772e-13 -2.0225e-16);
}
\endverbatim
Note: This fit is based on the small amount of data which is freely
available for the range 20-65degC and 1-100bar.
This equation of state is a much better fit for water and other liquids than
perfectFluid and in general polynomials for the reciprocal of the density
converge much faster than polynomials of the density. Currently rPolynomial is
quadratic in the temperature and linear in the pressure which is sufficient for
modest ranges of pressure typically encountered in CFD but could be extended to
higher order in pressure and/temperature if necessary. The other huge advantage
in formulating the equation of state in terms of the reciprocal of the density
is that coefficient mixing is simple.
Given these advantages over the perfectFluid equation of state the libraries and
tutorial cases have all been updated to us rPolynomial rather than perfectFluid
for liquids and water in particular.
solidChemistryModel is not implemented in a general way but specialised to form
the basis of the highly specific pyrolysis mode. The handling of reactions is
hard-coded for forward reactions only, the Jacobian was present but incomplete
so any ODE solvers requiring the Jacobian would either fail, diverge or produce
incorrect results. It is not clear if many or any parts of the
solidChemistryModel are correct, in particular there is no handling for the
solid surface area per unit volume. After a lot of refactoring work it has
become clear that solidChemistryModel needs a complete rewrite and can benefit
from all the recent development work done on the now more general
StandardChemistryModel.
This change adds representation of the shape of a dispersed phase. A
layer has been added to model the relationship between the
characteristic volume of a sizeGroup and its physical diameter.
Previously this relationship was represented by a constant form factor.
Currently, two shape models are available:
- spherical
- fractal (for modelling fractal agglomerates)
The latter introduces the average surface area to volume ratio, kappa,
of the entities in a size group as a secondary field-dependent internal
variable to the population balance equation, which makes the population
balance approach "quasi-"bivariate. From kappa and a constant mass
fractal dimension, a collisional diameter can be derived which affects
the coagulation rates computed by the following models:
- ballisticCollisions
- brownianCollisions
- DahnekeInterpolation
- turbulentShear
The fractal shape modelling also takes into account the effect of sintering
of primary particles on the surface area of the aggregate.
Further additions/changes:
- Time scale filtering for handling large drag and heat transfer
coefficients occurring for particles in the nanometre range
- Aerosol drag model based on Stokes drag with a Knudsen number based
correction (Cunningham correction)
- Reaction driven nucleation
- A complete redesign of the sizeDistribution functionObject
The functionality is demonstrated by a tutorial case simulating the
vapour phase synthesis of titania by titanium tetrachloride oxidation.
Patch contributed by Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden -
Rossendorf (HZDR) and VTT Technical Research Centre of Finland Ltd.
All reactingEulerFoam wall boiling tutorials have been replaced with
cases that are more representative of real applications.
The wall boiling tutorials for reactingTwoPhaseEulerFoam are:
RAS/wallBoiling:
Axi-symmetric wall boiling case with constant bubble diameter
RAS/wallBoilingPolyDisperse:
As wallBoiling, but with a homogenous class method population
balance for modelling the bubble diameters
RAS/wallBoilingIATE:
As wallBoiling, but with an interfacial area transport equation
for modelling the bubble diameters
The wall boiling tutorials for reactingMultiphaseEulerFoam are:
RAS/wallBoilingPolydisperseTwoGroups:
As wallBoiling, but with an inhomogenous class method population
balance for modelling the bubble diameters
Patch contributed by Juho Peltola, VTT.
Both the functionObject call context (the command line for postProcess, and the
controlDict path for run-time post-precessing) and the configuration file
context where the arguments are substituted are now printed in the error
message, e.g.
postProcess -func 'patchAverage(name=inlet, ields=(p U))'
generates the message
--> FOAM FATAL IO ERROR:
Essential value for keyword 'fields' not set in function entry
patchAverage(name=inlet, ields=(p U))
in command line postProcess -func patchAverage(name=inlet, ields=(p U))
Placeholder value is <field_names>
file: /home/dm2/henry/OpenFOAM/OpenFOAM-dev/etc/caseDicts/postProcessing/surfaceFieldValue/patchAverage from line 13 to line 17.
and with the following in controlDict
functions
{
#includeFunc patchAverage(name=inlet, ields=(p U))
}
generates the message
--> FOAM FATAL IO ERROR:
Essential value for keyword 'fields' not set in function entry
patchAverage(name=inlet, ields=(p U))
in file /home/dm2/henry/OpenFOAM/OpenFOAM-dev/tutorials/incompressible/pimpleFoam/RAS/pitzDaily/system/controlDict at line 55
Placeholder value is <field_names>
file: /home/dm2/henry/OpenFOAM/OpenFOAM-dev/etc/caseDicts/postProcessing/surfaceFieldValue/patchAverage from line 13 to line 17.
kappa is now obtained from the fluidThermo for laminar regions, the turbulence
model for turbulent regions and the solidThermo for solid regions. The "lookup"
option previously supported allowed for energy-temperature inconsistent and
incorrect specification of kappa and was not used. Without this incorrect
option there is now no need to specify a kappaMethod thus significantly
simplifying the use boundary conditions derived from temperatureCoupledBase.
Added new reaction rate fluxLimitedLangmuirHinshelwoodReactionRate which is a
variant of the standard LangmuirHinshelwoodReactionRate but with a surface flux
limiter dependent on the surface area per unit volume Av which can be supplied
either as a uniform value or a field name which is looked-up from the region
database (objectRegistry).
Description
Langmuir-Hinshelwood reaction rate for gaseous reactions on surfaces
including the optional flux limiter of Waletzko and Schmidt.
References:
\verbatim
Hinshelwood, C.N. (1940).
The Kinetics of Chemical Change.
Oxford Clarendon Press
Waletzko, N., & Schmidt, L. D. (1988).
Modeling catalytic gauze reactors: HCN synthesis.
AIChE journal, 34(7), 1146-1156.
\endverbatim
Now that the reaction system is separated from the mixture thermodynamics it is
possible to rationalise singleStepCombustion so that it instantiates a single
reaction as it should. This simplifies the code, maintenance and the user
interface not that the combustionProperties file contains a single reaction
rather than a list.
This allows much greater flexibility in the instantiation of reaction system
which may in general depend on fields other than the thermodynamic state. This
also simplifies mixture thermodynamics removing the need for the reactingMixture
and the instantiation of all the thermodynamic package combinations depending on
it.
which are now read directly from the thermophysicalProperties dictionary for
consistency with non-reacting mixture thermodynamics. The species thermo and
reactions lists can still be in separate files if convenient and included into
the thermophysicalProperties file using the standard dictionary #include.
This formalises the flexible and extensible OpenFOAM thermodynamics and reaction
format as the direct input to OpenFOAM solvers. The CHEMKIN format is still
supported by first converting to the OpenFOAM format using the chemkinToFoam
utility.
Added limiters for the phase temperatures to prevent divergence, and
monitors to report the minimum and maximum values. Removed the
setTimeStep functionObject as the temperature limiters make this
unnecessary. Dereased the number of energy correctors and set a higher
Courant number limit to reduce the execution-time of the case.
Patch contributed by Juho Peltola, VTT.
Refactored the function for scaling the size group volume fractions to
better handle situations in which their sum drifts away from unity.
Scaling is now turned on by default, and can be turned off in the
solution dictionary for the population balance.
Additional revision and renaming of *Polydisperse tutorials
Patch contributed by Institute of Fluid Dynamics,
Helmholtz-Zentrum Dresden - Rossendorf (HZDR)
This fix also required a generalization of the corresponding base class,
which allows the user to specify the number of daughter particles per
breakup event separately.
Patch contributed by Institute of Fluid Dynamics,
Helmholtz-Zentrum Dresden - Rossendorf (HZDR)
The various temporary fields used to create the nuTilda equation sources are now
internal fields to avoid unnecessary evaluation of boundary conditions, lowering
storage and reducing CPU time, particularly when running in parallel. These
temporary fields are now named with respect to the model so that they can be
cached conveniently and written as required.
The LESRegion field can now be contructed on demand if it is requested as a
cached temporary field and written out for diagnostics if needed, for example in
the tutorials/incompressible/pisoFoam/LES/motorBike tutorial:
cacheTemporaryObjects
(
SpalartAllmarasDDES:LESRegion
);
functions
{
writeCachedObjects
{
type writeObjects;
libs ("libutilityFunctionObjects.so");
writeControl writeTime;
writeOption anyWrite;
objects
(
SpalartAllmarasDDES:LESRegion
);
}
#include "cuttingPlane"
#include "streamLines"
#include "forceCoeffs"
}
For example in the combustion/coldEngineFoam/freePiston/0/p field the
internalField entry may be obtained from the include/caseSettings dictionary
using either a relative path:
internalField uniform $include/caseSettings!internalField/p;
or an absolute path:
internalField uniform ${$FOAM_CASE/0/include/caseSettings!internalField/p};
in which recursive substitution using ${...} is applied to expand the $FOAM_CASE
environment variable.
Arc-edges can now be specified with a sector angle (in degrees) and an
axis of the circle of which the arc forms a part. The new syntax is as
follows:
edges
(
arc <vertex-0> <vertex-1> <angle> (<axis-x> <axis-y> <axis-z>)
);
This is often more convenient than the alternative specification where a
third third point somewhere in the arc is given; it usually does not
require any additional calculation on the part of the user, and multiple
entries are very likely to be identical.
Which specification is used depends on the form of the entry that comes
after the two vertices. If the entry is a vector then it is assumed to
be a point in the arc; if it is scalar then is is taken to be the angle
and the axis is assumed to follow.
For example, to put a 90 degree arc between the vertices 12 and 13, at
(1 0 0) and (0 1 0) respectively, the following specification can now be
used:
edges
(
arc 12 13 90.0 (0 0 1)
);
This is equivalent to the existing point-in-arc speficiation below:
edges
(
arc 12 13 (0.707107 0.707107 0)
);
An edge's points are ordered on the perimeter of the circle according to
a right-hand screw rule on the given axis. Changing the the side of the
edge on which the arc is defined can therefore be achieved by reversing
either the edge or the direction of the axis.
If the given axis is not perpendicular to the line between the vertices,
then the arc gains some axial length and becomes a helix.
