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