Improves stability and convergence of systems in which drag dominates
e.g. small particles in high-speed gas flow.
Additionally a new ddtPhiCorr strategy is included in which correction
is applied only where the phases are nearly pure. This reduces
staggering patters near the free-surface of bubble-column simulations.
Allows the specification of a reference height, for example the height
of the free-surface in a VoF simulation, which reduces the range of p_rgh.
hRef is a uniformDimensionedScalarField specified via the constant/hRef
file, equivalent to the way in which g is specified, so that it can be
looked-up from the database. For example see the constant/hRef file in
the DTCHull LTSInterFoam and interDyMFoam cases.
Disadvantage is that the BC values have to be specified in terms of hU
rather than U. The alternative would be to add complex code to map h
and U BCs into the equivalent for hU.
Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1566
The implementation now correspond to the definitions in the readily
available reference:
http://personalpages.manchester.ac.uk/staff/david.d.apsley/specturb.pdf
in which a large number of linear and non-linear models are presented in
a clean and consistent manner. This has made re-implementation and
checking far easier than working from the original references which anyway
are no longer available for the LienCubicKE and ShihQuadraticKE models.
This is an experimental feature demonstrating the potential of MULES to
create bounded solution which are 2nd-order in time AND space.
Crank-Nicolson may be selected on U and/or alpha but will only be fully
2nd-order if used on both within the PIMPLE-loop to converge the
interaction between the flux and phase-fraction. Note also that
Crank-Nicolson may not be used with sub-cycling but all the features of
semi-implicit MULES are available in particular MULESCorr and
alphaApplyPrevCorr.
Examples of ddt specification:
ddtSchemes
{
default Euler;
}
ddtSchemes
{
default CrankNicolson 0.9;
}
ddtSchemes
{
default none;
ddt(alpha) CrankNicolson 0.9;
ddt(rho,U) CrankNicolson 0.9;
}
ddtSchemes
{
default none;
ddt(alpha) Euler;
ddt(rho,U) CrankNicolson 0.9;
}
ddtSchemes
{
default none;
ddt(alpha) CrankNicolson 0.9;
ddt(rho,U) Euler;
}
In these examples a small amount of off-centering in used to stabilize
the Crank-Nicolson scheme. Also the specification for alpha1 is via the
generic phase-fraction name to ensure in multiphase solvers (when
Crank-Nicolson support is added) the scheme is identical for all phase
fractions.
