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.
This development is back-ported from OpenFOAM-dev:
f78d33b634
1cacdf0d89