hybridVoidFraction

Syntax

Defined in couplingProperties dictionary.

voidfractionModel hybrid;
hybridProps
{
    hybridForceModel Switch;
    resolvedModel word;
    unresolvedModel word;
    writeActiveVfModel Switch;
    verbose Switch;
}

  • hybridForceModel = enable the hybrid force model (default: true)

  • resolvedModel = voidfraction model used for resolved particles (default: IB)

  • unresolvedModel = voidfraction model used for unresolved particles (default: bigParticle)

  • writeActiveVfModel = write a field that indicates which voidfraction model is active (default: false)

  • verbose = enable verbose terminal output (default: false)

Examples

voidfractionModel hybrid;
hybridProps
{
    resolvedModel   IB;
    unresolvedModel bigParticle;
}

IBProps
{
    see IB voidfraction model
    the voidfractionFieldName needs to be set
}

bigParticleProps
{
    see bigParticle voidfracion model
    the voidfractionFieldName needs to be set
}

Description

The hybrid voidFraction model can be used in CFD-DEM setups where both unresolved (substantially smaller than a CFD cell) and resolved (substantially larger than a CFD cell) particles are present.

The model is specifically designed for the resolved IB and the unresolved bigParticle and divided voidfraction models. The properties for the two selected voidfraction models need to be defined in the couplingProperties dictionary as well, and for both an unique voidfractionFieldName needs to be assigned. Internally the hybrid voidfraction model will create these two voidfraction fields, which will be used by the resolved (ShirgaonkarIB) and unresolved (KochHillDrag) force models after setting the correct voidfractionFieldName for these force models as well.

The minimum number of cells per particle (as set in the IB voidfraction model) will be used to flag particles as resolved or unresolved. This flag will be used to set the hybrid voidfraction field from the resolved and unresolved voidfraction fields. Next, this hybrid voidfraction field is used by the cfdemSolverPimple. Furthermore, the resolved/unresolved flag is used to determine which force model is active in a CFD cell.

Restrictions

For now the hybrid voidfraction model is limited to (tested for) the following settings: IB for the resolvedModel and bigParticle or divided for the unresolvedModel. For stability it might be required to increase the nCorrector value (up to 10) in the PISO sub-dictionary of CFD/system/fvSolution.