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.
The previous time-step compression flux is not valid/accurate on the new mesh
and it is better to re-calculate it rather than map it from the previous mesh to
the new mesh.
Avoids slight phase-fraction unboundedness at entertainment BCs and improved
robustness.
Additionally the phase-fractions in the multi-phase (rather than two-phase)
solvers are adjusted to avoid the slow growth of inconsistency ("drift") caused
by solving for all of the phase-fractions rather than deriving one from the
others.
e.g. in the reactingFoam/laminar/counterFlowFlame2DLTS tutorial:
PIMPLE
{
momentumPredictor no;
nOuterCorrectors 1;
nCorrectors 1;
nNonOrthogonalCorrectors 0;
maxDeltaT 1e-2;
maxCo 1;
alphaTemp 0.05;
alphaY 0.05;
Yref
{
O2 0.1;
".*" 1;
}
rDeltaTSmoothingCoeff 1;
rDeltaTDampingCoeff 1;
}
will limit the LTS time-step according to the rate of consumption of 'O2'
normalized by the reference mass-fraction of 0.1 and all other species
normalized by the reference mass-fraction of 1. Additionally the time-step
factor of 'alphaY' is applied to all species. Only the species specified in the
'Yref' sub-dictionary are included in the LTS limiter and if 'alphaY' is omitted
or set to 1 the reaction rates are not included in the LTS limiter.
Combined 'dQ()' and 'Sh()' into 'Qdot()' which returns the heat-release rate in
the normal units [kg/m/s3] and used as the heat release rate source term in
the energy equations, to set the field 'Qdot' in several combustion solvers
and for the evaluation of the local time-step when running LTS.
Added the interfacial pressure-work terms according to:
Ishii, M., Hibiki, T.,
Thermo-fluid dynamics of two-phase flow,
ISBN-10: 0-387-28321-8, 2006
While this is the most common approach to handling the interfacial
pressure-work it introduces numerical stability issues in regions of low
phase-fraction and rapid flow deformation. To alleviate this problem an
optional limiter may be applied to the pressure-work term in either of
the energy forms. This may specified in the
"thermophysicalProperties.<phase>" file, e.g.
pressureWorkAlphaLimit 1e-3;
which sets the pressure work term to 0 for phase-fractions below 1e-3.
For particularly unstable cases a limit of 1e-2 may be necessary.
Added 'READ_IF_PRESENT' option to support overriding of the default BCs
for complex problems requiring special treatment of Udm at boundaries.
Resolves bug-report http://bugs.openfoam.org/view.php?id=2317
In many publications and Euler-Euler codes the pressure-work term in the
total enthalpy is stated and implemented as -alpha*dp/dt rather than the
conservative form derived from the total internal energy equation
-d(alpha*p)/dt. In order for the enthalpy and internal energy equations
to be consistent this error/simplification propagates to the total
internal energy equation as a spurious additional term p*d(alpha)/dt
which is included in the OpenFOAM Euler-Euler solvers and causes
stability and conservation issues.
I have now re-derived the energy equations for multiphase flow from
first-principles and implemented in the reactingEulerFoam solvers the
correct conservative form of pressure-work in both the internal energy
and enthalpy equations.
Additionally an optional limiter may be applied to the pressure-work
term in either of the energy forms to avoid spurious fluctuations in the
phase temperature in regions where the phase-fraction -> 0. This may
specified in the "thermophysicalProperties.<phase>" file, e.g.
pressureWorkAlphaLimit 1e-3;
which sets the pressure work term to 0 for phase-fractions below 1e-3.
Previously the inlet flow of phase 1 (the phase solved for) is corrected
to match the inlet specification for that phase. However, if the second
phase is also constrained at inlets the inlet flux must also be
corrected to match the inlet specification.
to handle the size of bubbles created by boiling. To be used in
conjunction with the alphatWallBoilingWallFunction boundary condition.
The IATE variant of the wallBoiling tutorial case is provided to
demonstrate the functionality:
tutorials/multiphase/reactingTwoPhaseEulerFoam/RAS/wallBoilingIATE
Contributed by Juho Peltola, VTT
Notable changes:
1. The same wall function is now used for both phases, but user must
specify phaseType ‘liquid’ or ‘vapor’
2. Runtime selectable submodels for:
- wall heat flux partitioning between the phases
- nucleation site density
- bubble departure frequency
- bubble departure diameter
3. An additional iteration loop for the wall boiling model in case
the initial guess for the wall temperature proves to be poor.
The wallBoiling tutorial has been updated to demonstrate this new functionality.
to ensure 'patchType' is set as specified.
Required substantial change to the organization of the reading of the
'value' entry requiring careful testing and there may be some residual
issues remaining. Please report any problems with the reading and
initialization of patch fields.
Resolves bug-report http://bugs.openfoam.org/view.php?id=2266
Renamed the original 'laminar' model to 'Stokes' to indicate it is a
linear stress model supporting both Newtonian and non-Newtonian
viscosity.
This general framework will support linear, non-linear, visco-elastic
etc. laminar transport models.
For backward compatibility the 'Stokes' laminar stress model can be
selected either the original 'laminar' 'simulationType'
specification in turbulenceProperties:
simulationType laminar;
or using the new more general 'laminarModel' specification:
simulationType laminar;
laminar
{
laminarModel Stokes;
}
which allows other laminar stress models to be selected.
Required to support LTS with the -postProcess option with sub-models dependent on ddt
terms during construction, in particular reactingTwoPhaseEulerFoam.
