mirror of
https://github.com/ParticulateFlow/CFDEMcoupling-PFM.git
synced 2025-12-08 06:37:44 +00:00
98 lines
3.3 KiB
Plaintext
98 lines
3.3 KiB
Plaintext
"CFDEMproject Website"_lws - "Main Page"_main :c
|
|
|
|
:link(lws,http://www.cfdem.com)
|
|
:link(main,CFDEMcoupling_Manual.html)
|
|
|
|
:line
|
|
|
|
voidFractionModel divided command :h3
|
|
|
|
[Syntax:]
|
|
|
|
Defined in "couplingProperties"_CFDEMcoupling_dicts.html#couplingProperties
|
|
dictionary.
|
|
|
|
voidFractionModel divided;
|
|
dividedProps
|
|
\{
|
|
alphaMin number1;
|
|
interpolation;
|
|
weight number2;
|
|
porosity number3;
|
|
procBoundaryCorrection switch1;
|
|
verbose;
|
|
\} :pre
|
|
|
|
{number1} = minimum limit for void fraction :ulb,l
|
|
{interpolation} = flag to interpolate void fraction to particle positions (normally off) :l
|
|
{number2} = (optional) scaling of the particle volume to account for porosity or agglomerations. :l
|
|
{number3} = (optional) diameter of the particle's representation is artificially increased according to {number2} * Vparticle, volume remains unaltered! :l
|
|
{switch1} = (optional, default false) allow for correction at processor boundaries. This requires the use of engineIB and vice versa. :l
|
|
{verbose} = (optional, default false) flag for debugging output :l
|
|
:ule
|
|
|
|
[Examples:]
|
|
|
|
voidFractionModel divided;
|
|
dividedProps
|
|
\{
|
|
alphaMin 0.2;
|
|
\} :pre
|
|
|
|
[Description:]
|
|
|
|
The {divided} void fraction model is supposed to be used when a particle (or its
|
|
representation) is in the size range of a CFD cell. Satellite points are used to
|
|
divide the particle's volume to the touched cells.
|
|
|
|
The particle has radius R and its volume is divided into 29 non-overlapping
|
|
regions of equal volume. The centroids of these volumes are then used to
|
|
reproduce each volume. The first volume is a sphere with the center coinciding
|
|
with the particle center. The radius of this subsphere can be found as follows:
|
|
|
|
:c,image(Eqs/voidfractionModel_divided_pic2.png)
|
|
|
|
The rest of the volume is a spherical layer that is divided into 2 layers of
|
|
equal volume. Position of the border between these two spherical layers in
|
|
radial direction can be easily obtained:
|
|
|
|
:c,image(Eqs/voidfractionModel_divided_pic3.png)
|
|
|
|
Each of these spherical layers is later divided into 14 elements of equal volume.
|
|
Position of the centroid point in radial direction of each volume in the first
|
|
spherical layer is as follows
|
|
|
|
:c,image(Eqs/voidfractionModel_divided_pic4.png)
|
|
|
|
Similarly, for the second spherical layer remembering that the external radius
|
|
is the particle radius:
|
|
|
|
:c,image(Eqs/voidfractionModel_divided_pic5.png)
|
|
|
|
The region of influence of a particle can be increased artificially by
|
|
{porosity}, which blows up the particles, but keeps their volume (for
|
|
void fraction calculation) constant.
|
|
|
|
The particle volume occupied in the CFD domain can be adjusted by the parameter
|
|
{weight}, using
|
|
|
|
:c,image(Eqs/voidfractionModel_divided_pic6.png).
|
|
|
|
In the basic implementation of solvers, the void fraction is calculated based on
|
|
all particles. Depending on the solver used, the void fraction calculation is
|
|
also performed for a certain type of particles.
|
|
The void fraction calculation is based on a three-step approach (reset, set and
|
|
interpolate), i.e. the void fraction is time interpolated from a previous and a
|
|
next void fraction field. Appropriate names for these fields have to be
|
|
specified in the sub-dictionaries voidFracFieldNamesPrev and
|
|
voidFracFieldNamesNext in the couplingProperties dictionary.
|
|
|
|
[Restrictions:]
|
|
|
|
none
|
|
|
|
[Related commands:]
|
|
|
|
"voidFractionModel"_voidFractionModel.html
|
|
|