The built-in explicit symplectic integrator has been replaced by a
general framework supporting run-time selectable integrators. Currently
the explicit symplectic, implicit Crank-Nicolson and implicit Newmark
methods are provided, all of which are 2nd-order in time:
Symplectic 2nd-order explicit time-integrator for 6DoF solid-body motion:
Reference:
Dullweber, A., Leimkuhler, B., & McLachlan, R. (1997).
Symplectic splitting methods for rigid body molecular dynamics.
The Journal of chemical physics, 107(15), 5840-5851.
Can only be used for explicit integration of the motion of the body,
i.e. may only be called once per time-step, no outer-correctors may be
applied. For implicit integration with outer-correctors choose either
CrankNicolson or Newmark schemes.
Example specification in dynamicMeshDict:
solver
{
type symplectic;
}
Newmark 2nd-order time-integrator for 6DoF solid-body motion:
Reference:
Newmark, N. M. (1959).
A method of computation for structural dynamics.
Journal of the Engineering Mechanics Division, 85(3), 67-94.
Example specification in dynamicMeshDict:
solver
{
type Newmark;
gamma 0.5; // Velocity integration coefficient
beta 0.25; // Position integration coefficient
}
Crank-Nicolson 2nd-order time-integrator for 6DoF solid-body motion:
The off-centering coefficients for acceleration (velocity integration) and
velocity (position/orientation integration) may be specified but default
values of 0.5 for each are used if they are not specified. With the default
off-centering this scheme is equivalent to the Newmark scheme with default
coefficients.
Example specification in dynamicMeshDict:
solver
{
type CrankNicolson;
aoc 0.5; // Acceleration off-centering coefficient
voc 0.5; // Velocity off-centering coefficient
}
Both the Newmark and Crank-Nicolson are proving more robust and reliable
than the symplectic method for solving complex coupled problems and the
tutorial cases have been updated to utilize this.
In this new framework it would be straight forward to add other methods
should the need arise.
Henry G. Weller
CFD Direct
read in the construction from dictionary.
It is important that the initial value is obtained from the table
provided to avoid the user having to evaluate a consistent one or risk
the code crashing from a very sudden change in the value.
For explicit motion (and the first iteration of iterative motion
correction) the 2nd-order symplectic motion integrator is used.
For iterative correction a form of lagged Crank-Nicolson is used in
which the current time-step values correspond to the current iteration.
This converges to a 2nd-order implicit solution.
Solidification phase change model where all film mass is converted when the
local temperature > activation temperature. The latent heat is
assumed to be removed by heat-transfer to the wall.
Avoids problems with overlapping communicationbetween these reductions
and the calculation of deltaCoeffs. This is a temporary fix while code
reorganizations are undertaken to ensure the globalMeshData is updated
before deltaCoeffs are requested.
Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1780
