The new fvModels is a general interface to optional physical models in the
finite volume framework, providing sources to the governing conservation
equations, thus ensuring consistency and conservation. This structure is used
not only for simple sources and forces but also provides a general run-time
selection interface for more complex models such as radiation and film, in the
future this will be extended to Lagrangian, reaction, combustion etc. For such
complex models the 'correct()' function is provided to update the state of these
models at the beginning of the PIMPLE loop.
fvModels are specified in the optional constant/fvModels dictionary and
backward-compatibility with fvOption is provided by reading the
constant/fvOptions or system/fvOptions dictionary if present.
The new fvConstraints is a general interface to optional numerical constraints
applied to the matrices of the governing equations after construction and/or to
the resulting field after solution. This system allows arbitrary changes to
either the matrix or solution to ensure numerical or other constraints and hence
violates consistency with the governing equations and conservation but it often
useful to ensure numerical stability, particularly during the initial start-up
period of a run. Complex manipulations can be achieved with fvConstraints, for
example 'meanVelocityForce' used to maintain a specified mean velocity in a
cyclic channel by manipulating the momentum matrix and the velocity solution.
fvConstraints are specified in the optional system/fvConstraints dictionary and
backward-compatibility with fvOption is provided by reading the
constant/fvOptions or system/fvOptions dictionary if present.
The separation of fvOptions into fvModels and fvConstraints provides a rational
and consistent separation between physical and numerical models which is easier
to understand and reason about, avoids the confusing issue of location of the
controlling dictionary file, improves maintainability and easier to extend to
handle current and future requirements for optional complex physical models and
numerical constraints.
Field corrections are effectively explicit constraints applied to the field
after solution rather than to the equation and it significantly simplifies the
implementation to treat them as a special case of constraints. To implement
this the fvOption::correct(<field>) function has been renamed
fvOption::constrain(<field>) and uses constrainsField and constrainedFields.
The sub-loops of the solution control are now named more consistently,
with ambiguously named methods such as finalIter replaced with ones
like finalPimpleIter, so that it is clear which loop they represent.
In addition, the final logic has been improved so that it restores state
after a sub-iteration, and so that sub-iterations can be used on their
own without an outer iteration in effect. Previously, if the
non-orthogonal loop were used outside of a pimple/piso iteration, the
final iteration would not execute with final settings.
Registration occurs when the temporary field is transferred to a non-temporary
field via a constructor or if explicitly transferred to the database via the
regIOobject "store" methods.
The solution controls have been rewritten for use in multi-region
solvers, and PIMPLE fluid/solid solution controls have been implemented
within this framework.
PIMPLE also now has time-loop convergence control which can be used to
end the simulation once a certain initial residual is reached. This
allows a PIMPLE solver to run with equivalent convergence control to a
SIMPLE solver. Corrector loop convergence control is still available,
and can be used at the same time as the time-loop control.
The "residualControl" sub-dictionary of PIMPLE contains the residual
values required on the first solve of a time-step for the simulation to
end. This behaviour is the same as SIMPLE. The
"outerCorrectorResidualControl" sub-dictionary contains the tolerances
required for the corrector loop to exit. An example specification with
both types of control active is shown below.
PIMPLE
{
// ...
residualControl
{
p 1e-3;
U 1e-4;
"(k|epsilon|omega)" 1e-3;
}
outerCorrectorResidualControl
{
U
{
tolerance 1e-4;
relTol 0.1;
}
"(k|epsilon|omega)"
{
tolerance 1e-3;
relTol 0.1;
}
}
}
Note that existing PIMPLE "residualControl" entries will need to be
renamed "outerCorrectorResidualControl".
Application within a solver has also changed slightly. In order to have
convergence control for the time loop as a whole, the
solutionControl::loop(Time&) method (or the equivalent run method) must
be used; i.e.,
while (simple.loop(runTime))
{
Info<< "Time = " << runTime.timeName() << nl << endl;
// solve ...
}
or,
while (pimple.run(runTime))
{
// pre-time-increment operations ...
runTime ++;
Info<< "Time = " << runTime.timeName() << nl << endl;
// solve ...
}
In early versions of OpenFOAM the scalar limits were simple macro replacements and the
names were capitalized to indicate this. The scalar limits are now static
constants which is a huge improvement on the use of macros and for consistency
the names have been changed to camel-case to indicate this and improve
readability of the code:
GREAT -> great
ROOTGREAT -> rootGreat
VGREAT -> vGreat
ROOTVGREAT -> rootVGreat
SMALL -> small
ROOTSMALL -> rootSmall
VSMALL -> vSmall
ROOTVSMALL -> rootVSmall
The original capitalized are still currently supported but their use is
deprecated.
This ensures that the fvOptions are constructed for the -postProcessing option
so that functionObjects which process fvOption data operate correctly in this
mode.
to have the prefix 'write' rather than 'output'
So outputTime() -> writeTime()
but 'outputTime()' is still supported for backward-compatibility.
Also removed the redundant secondary-writing functionality from Time
which has been superseded by the 'writeRegisteredObject' functionObject.
e.g. (fvc::interpolate(HbyA) & mesh.Sf()) -> fvc::flux(HbyA)
This removes the need to create an intermediate face-vector field when
computing fluxes which is more efficient, reduces the peak storage and
improved cache coherency in addition to providing a simpler and cleaner
API.
fvOptions are transferred to the database on construction using
fv::options::New which returns a reference. The same function can be
use for construction and lookup so that fvOptions are now entirely
demand-driven.
The abstract base-classes for fvOptions now reside in the finiteVolume
library simplifying compilation and linkage. The concrete
implementations of fvOptions are still in the single monolithic
fvOptions library but in the future this will be separated into smaller
libraries based on application area which may be linked at run-time in
the same manner as functionObjects.
Added calls to setFluxRequired for p in all incompressible solvers which
avoids the need to add fluxRequired entries in fvSchemes dictionary.
Will add calls to setFluxRequired to the rest of the solvers.
fvOptions does not have the appropriate structure to support MRF as it
is based on option selection by user-specified fields whereas MRF MUST
be applied to all velocity fields in the particular solver. A
consequence of the particular design choices in fvOptions made it
difficult to support MRF for multiphase and it is easier to support
frame-related and field related options separately.
Currently the MRF functionality provided supports only rotations but
the structure will be generalized to support other frame motions
including linear acceleration, SRF rotation and 6DoF which will be
run-time selectable.
The Phi field is read if available otherwise created automatically with
boundary conditions obtained automatically from the pressure field if
available (with optional name) otherwise inferred from the velocity
field. Phi Laplacian scheme and solver specification are required. See
tutorials for examples.
