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.
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.
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.
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
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)
This implicit isotropic damping function relaxes the velocity field towards a
specified uniform value which can be set to (0 0 0) if no flow is required.
This is particularly appropriate to damp the waves in a closed wave tank with no
mean flow.
Testing on the interFoam wave has shown that for this simple case with uniform
mean flow the new isotropicDamping fvOption provides more rapid and complete
damping than the original verticalDamping.
Implementation of the Giesekus model for visco-elasticity, derived from the new
generalised form of the Maxwell model which now support additional sources.
Giesekus, H., 1982.
A simple constitutive equation for polymer fluids based on the
concept of deformation-dependent tensional mobility.
J. Non-Newton. Fluid. 11, 69–109.
This implementation is instantiated for incompressible, compressible and VoF
two-phase flow.
The keyword which selects how the subset over which the function
operates is generated has been renamed to "selectionMode", to make it
more consistent with other parts of the OpenFOAM (e.g., fvOptions). It
can still take the value "all" or "cellZone". A cell zone is now
specified with a "cellZone", again for consistency.
Error messaging has also been overhauled.
Patch contributed by Institute of Fluid Dynamics,
Helmholtz-Zentrum Dresden - Rossendorf (HZDR)
A number of improvements have been made to the population balance phase
change drift model.
- The model now checks the ordering of the phase pairs and changes the
sign of the drift rate accordingly.
- The phase change mass flux and weights are calculated for each
velocity group, so the drift rate and phase change mass flux should be
consistent for each velocity group.
- By default the phase change mass flux is distributed between the size
groups based on the interfacial area of each group. For backward
compatibility number weighting can be enabled with a new
"numberWeighted" option.
The model now requires the user to provide a list of phase pairs in the
usual parenthesised form, rather than using the name. For example:
phaseChange
{
pairs ((gas and liquid));
}
Patch contributed by Juho Peltola, VTT.
The Qdot field has been removed from all reacting solvers, in favour of
computing on the fly whenever it is needed. It can still be generated
for post-processing purposes by means of the Qdot function object. This
change reduces code duplication and storage for all modified solvers.
The Qdot function object has been applied to a number of tutorials in
order to retain the existing output.
A fix to Qdot has also been applied for multi-phase cases.
With the inclusion of boundary layer modelling in the gas, the
separation of wave perturbation from and mean flow became less useful,
and potentially prevents further extension to support similar boundary
layer modelling in the liquid.
The mean velocity entry, UMean, is now needed in the
constant/waveProperties file rather than in the waveVelocity boundary
condition.
In order to increase the flexibility of the wave library, the mean flow
handling has been removed from the waveSuperposition class. This makes
waveSuperposition work purely in terms of perturbations to a mean
background flow.
The input has also been split, with waves now defined as region-wide
settings in constant/waveProperties. The mean flow parameters are sill
defined by the boundary conditions.
The new format of the velocity boundary is much simpler. Only a mean
flow velocity is required.
In 0/U:
boundaryField
{
inlet
{
type waveVelocity;
UMean (2 0 0);
}
// etc ...
}
Other wave boundary conditions have not changed.
The constant/waveProperties file contains the wave model selections and
the settings to define the associated coordinate system and scaling
functions:
In constant/waveProperties:
origin (0 0 0);
direction (1 0 0);
waves
(
Airy
{
length 300;
amplitude 2.5;
phase 0;
angle 0;
}
);
scale table ((1200 1) (1800 0));
crossScale constant 1;
setWaves has been changed to use a system/setWavesDict file rather than
relying on command-line arguments. It also now requires a mean velocity
to be specified in order to prevent ambiguities associated with multiple
inlet patches. An example is shown below:
In system/setWavesDict:
alpha alpha.water;
U U;
liquid true;
UMean (1 0 0);
This is to make it clear that the value supplied is the scalar mean
velocity normal to the patch, and to distinguish it from other instances
of the keyword "UMean" which take a vector quantity.
The Scaled Function1 removes the need for classes to hold both a value
and a ramping function. If it is desired to ramp up a velocity up to
(10 0 0) over the space of 5 seconds, that can be achieved as follows:
velocity
{
type scale;
scale
{
type halfCosineRamp;
duration 5;
}
value (10 0 0);
}
Also, as a result of this change, the velocityRamping fvOption has
become a general acceleration source, based on a velocity Function1. It
has therefore been renamed accelerationSource.
