The Volume Fraction Reinitialization model allows you to increase or
decrease the interface sharpness by reinitializing the volume fraction field of the
solution.
The volume fraction reinitialization
mechanism in Simcenter STAR-CCM+ allows you to control
the interface sharpness by specifying a target interface width for the reinitialization
of the volume fraction field. The reinitialization is based on user-defined metrics for
the volume fraction gradients, introduced to monitor and identify smeared interfaces.
Once a certain level of smearing is exceeded, reinitialization is initiated. You can
also trigger the initialization at different instances during the simulation. Table 1. Volume Fraction
Reinitialization Model Reference
| Theory |
Volume Fraction
Reinitialization |
| Provided By |
|
| Example Node Path |
|
| Requires |
- Space:
Axisymmetric, Two
Dimensional, or Three
Dimensional
- Time:
Steady, Implicit
Unsteady, PISO
Unsteady, or Explicit
Unsteady
Multiphase
simulation:
- Material: Multiphase
- Multiphase
Model: Volume of Fluid
(VOF)
- Flow:
Segregated Flow*
|
| Properties |
None. |
| Activates |
Model Controls (child nodes) |
Target Interface Width See Target Interface Width
Properties. |
| Solvers |
Volume Fraction
Reinitialization |
Target Interface Width
Properties
-
- Method
- Specifies the method for defining the target
interface width
in Eqn. (2621), which is proportional to
number of cells. The recommended range is [0.1, 2]. A value of zero disables
the volume fraction reinitialization.
- Constant—the specified
target interface width is applied to all the cells.
- Field Function—allows you
to specify a spatially varying target interface width.
The following images show the volume fraction solution for different
values of the Target Interface Width after reinitialization.
| Target
Interface Width = 2 |
Target
Interface Width = 1 |
Target
Interface Width = 0.2 |
|
|
|
Volume Fraction
Reinitialization Solver Properties
- Under-Relaxation
Factor
- At each
iteration, this property governs the extent to which the newly computed
solution supplants the old solution. The default value is 1.
- Solver
Frozen
- When On, the solver does
not update any quantity during an iteration. It is Off by default.
This is a debugging option that can result in non-recoverable errors and
wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.
- Temporary Storage Retained
- When
On,
Simcenter STAR-CCM+ retains additional field data that the solver generates during an iteration. The particular data retained depends on the solver, and becomes available as field functions during subsequent iterations.
Off by default.
- Trigger
- Defines how
often volume reinitialization takes place.
- Enabled—when activated, allows you
to specify different forms of volume fraction reinitialization
triggers.
- Trigger set to one of the
following:
| Trigger |
Corresponding Method Node |
| Iteration Applicable
only for the steady time solver. |
Iteration FrequencySpecify the
number of iterations for reinitialization as well as the start
and stop iterations. |
| Time
Step Applicable
only for the unsteady time solver. |
Time-Step FrequencySpecify the
number of time-steps for reinitialization as well as the start
and stop time-steps. |
| Delta
Time Applicable
only for the unsteady time solver. |
Delta Time FrequencySpecify the
time interval delta time for reinitialization as well as the
start and stop time. |
| Update
Event Applicable
for both steady and unsteady time solvers. |
Event Frequency
Select one
Update
Event from the events defined within the node. |
-
| Note | For unsteady
simulations, volume fraction reinitialization is triggered at the
beginning of each time-step. |
