The calculations for mixture rho and U have been changed so that they
represent phase-averaged quantities over the moving phases only.
The mixture density is used as part of the pressure solution to
calculate buoyancy forces. The pressure within a stationary phase is
considered to be decoupled from the moving phases; i.e., it is
considered self-supporting. Therefore the stationary phase density
should not form a part of buoyancy calculations. This change to the
definition of mixture density ensures this.
Lookup of models associated with unordered phase pairs now searches for
both possible pair names; e.g. gasAndLiquid and liquidAndGas.
Patch contributed by Institute of Fluid Dynamics, Helmholtz-Zentrum
Dresden - Rossendorf (HZDR)
The nonRandomTwoLiquid and Roult interface composition models have been
instantiated (and updated so that they compile), and a fuller set of
multi-component liquids and multi-component and reacting gases have been
used.
The selection name of the saturated and nonRandomTwoLiquid models have
also been changed to remove the capitalisation from the first letter, as
is consistent with other sub-models that are not proper nouns.
Streamlines can now be tracked in both directions from the set of
initial locations. The keyword controlling this behaviour is
"direction", which can be set to "forward", "backward" or "both".
This new keyword superseeds the "trackForward" entry, which has been
retained for backwards compatibility.
For compatibility with all the mesh and related classes in OpenFOAM The 'normal'
function of the 'triangle', 'triFace' and 'face' classes now returns the unit
normal vector rather than the vector area which is now provided by the 'area'
function.
This model transfers a dispersed droplet phase to a film phase at a rate
relative to its intersection with a third phase. The third phase is
termed the "surface". It can be enabled in constant/phaseProperties as
follows:
phaseTransfer
(
(droplets and film)
{
type deposition;
droplet droplets;
surface solid;
efficiency 0.1;
}
);
The efficiency is an empirical factor which represents a reduction in
collisions as a result of droplets flowing around the surface phase and
not coalescing on impact.
This work was supported by Georg Skillas and Zhen Li, at Evonik
An additional layer has been added into the phase system hierarchy which
facilitates the application of phase transfer modelling. These are
models which exchange mass between phases without the thermal coupling
that would be required to represent phase change. They can be thought of
as representation changes; e.g., between two phases representing
different droplet sizes of the same physical fluid.
To facilitate this, the heat transfer phase systems have been modified
and renamed and now both support mass transfer. The two sided version
is only required for derivations which support phase change.
The following changes to case settings have been made:
- The simplest instantiated phase systems have been renamed to
basicTwoPhaseSystem and basicMultiphaseSystem. The
heatAndMomentumTransfer*System entries in constant/phaseProperties files
will need updating accordingly.
- A phaseTransfer sub-model entry will be required in the
constant/phaseProperties file. This can be an empty list.
- The massTransfer switch in thermal phase change cases has been renamed
phaseTransfer, so as not to be confused with the mass transfer models
used by interface composition cases.
This work was supported by Georg Skillas and Zhen Li, at Evonik
Description
This boundary condition extrapolates field to the patch using the near-cell
values and adjusts the distribution to match the specified, optionally
time-varying, mean value. This extrapolated field is applied as a
fixedValue for outflow faces but zeroGradient is applied to inflow faces.
This boundary condition can be applied to pressure when inletOutlet is
applied to the velocity so that a zeroGradient condition is applied to the
pressure at inflow faces where the velocity is specified to avoid an
unphysical over-specification of the set of boundary conditions.
Usage
\table
Property | Description | Required | Default value
meanValue | mean value Function1 | yes |
phi | Flux field name | no | phi
\endtable
Example of the boundary condition specification:
\verbatim
<patchName>
{
type fixedMeanOutletInlet;
meanValue 1.0;
}
\endverbatim
See also
Foam::fixedMeanFvPatchField
Foam::outletInletFvPatchField
Foam::Function1Types
The prghPressureFvPatchScalarField, prghTotalPressureFvPatchScalarField and
prghUniformDensityHydrostaticPressure p_rgh boundary conditions are now derived
from the corresponding pressure boundary conditions using the
PrghPressureFvPatchScalarField template.
Blended models are now registered and can be looked up in the same way
as regular interfacial models via the phaseSystem::lookupSubModel
method. For example, to access the blended drag model, the following
code could be used:
const BlendedInterfacialModel<dragModel>& drag =
fluid.lookupSubModel<BlendedInterfacialModel<dragModel>>
(
phasePair(gas, liquid)
);
Here, "fluid" is the phase system, and "gas" and "liquid" are the phase
models between which the blended drag model applies.
The implementation of the porousBafflePressure BC was incorrect in OpenFOAM-2.4
and earlier and corrected during the turbulence modeling rewrite for
OpenFOAM-3.0. This update introduced the density scaling required for the
definition of pressure in interFoam which requires the porosity coefficients to
be reduced.
Resolves bug-report https://bugs.openfoam.org/view.php?id=2890
Also added tutorial case demonstrating usage. Note that the new drag
models are symmetric and should be used without any blending.
This work was supported by Georg Skillas and Zhen Li, at Evonik
It may be convenient to specify these directions un-normalized so it is
necessary to normalize them before they are used to calculate the force
coefficients.
which simplifies the reactingEulerFoam populationBalance test cases.
Patch contributed by Institute of Fluid Dynamics, Helmholtz-Zentrum
Dresden - Rossendorf (HZDR)
Sub-model blending should be set such that the sum of all the blending
coefficients equals one. If there are three models specified for a phase
pair (e.g., (air in water), (water in air) and (air and water)), then
the sum-to-one constraint is guaranteed by the blending functions.
Frequently, however, the symmetric model ((air and water) in this
example) is omitted. In that case, the blending coefficients should be
selected so that the sum of just the two non-symmetric coefficients
equal one.
In the case of linear blending, this means setting the minimum partially
continuous alpha to one-minus the fully continuous value of the opposite
phase. For example:
blending
{
default
{
type linear;
minFullyContinuousAlpha.air 0.7;
minPartlyContinuousAlpha.air 0.3;
minFullyContinuousAlpha.water 0.7;
minPartlyContinuousAlpha.water 0.3;
}
}
The reactingTwoPhaseEulerFoam and reactingMultiPhaseEulerFoam tutorials
have been modified to adhere to this principle.
Two new phase models have been added as selectable options for
reactingMultiphaseEulerFoam; pureStationaryPhaseModel and
pureStationaryIsothermalPhaseModel. These phases do not store a
velocity and their phase fractions remain constant throughout the
simulation. They are intended for use in modelling static particle beds
and other forms of porous media by means of the existing Euler-Euler
transfer models (drag, heat transfer, etc...).
Note that this functionality has not been extended to
reactingTwoPhaseEulerFoam, or the non-reacting *EulerFoam solvers.
Additional maintenance work has been carried out on the phase model
and phase system structure. The system can now loop over subsets of
phases with specific functionality (moving, multi-component, etc...) in
order to avoid testing for the existence of equations or variables in
the top level solver. The mass transfer handling and it's effect on
per-phase source terms has been refactored to reduce duplication. Const
and non-const access to phase properties has been formalised by renaming
non-const accessors with a "Ref" suffix, which is consistent with other
recent developments to classes including tmp and GeometricField, among
others. More sub-modelling details have been made private in order to
reduce the size of interfaces and improve abstraction.
This work was supported by Zhen Li, at Evonik
MULES and CMULES have been extended so that the limits can be supplied
as fields. These arguments are templated so that zeroField, oneField or
UniformField<scalar> can be used in place of a scalar value with no
additional overhead. The flux argument has been removed from the
unlimited CMULES correct functions in order to make this templating
possible.
An additional form of limit sum has also been added to MULES. This
limits the flux sum by ofsetting in proportion to the phase fraction,
rather than by reducing the magnitude of the fluxes with the same sign
as the imbalance. The new procedure makes it possible to limit the flux
sum in the presence of constraints without encountering a divide by
zero.
The initial set of cases in the test directory are aimed at testing the
reactingEulerFoam populationBalance functionality.
Patch contributed by Institute of Fluid Dynamics, Helmholtz-Zentrum
Dresden - Rossendorf (HZDR) and VTT Technical Research Centre of Finland Ltd.
Integrated with the "tutorials" functionality by CFD Direct Ltd.
