StokesClumpDrag

Syntax

Defined in couplingProperties dictionary.

particleShapeType multisphere;
forceModels
(
    StokesClumpDrag
);
StokesClumpDragProps
{
    velFieldName         "U";
    voidfractionFieldName "voidfraction";
    granVelFieldName     "Us";
    ignoreDrag           switch;
    ignoreTorque         switch;
    useVoidfractionCorrection switch;
    vpIterMax            label;
    relTolDrag           scalar;
    relTolTorque         scalar;
    CdTorquePrimeDiagonal vector;
    periodicHalo         vector;
    implicitRotation     switch;
    useVoidfractionCorrection switch;

    // (optional) forceSubModel switches
    scaleDrag            scalar;
    scaleTorque          scalar;
    scaleDH              scalar;
    implForceDEM         switch;
    treatForceExplicit   switch;
    verbose              switch;
    interpolation        switch;
    voidageFunctionDiFelice switch;
    voidageFunctionRong  switch;
    voidageFunctionTang  switch;
};

  • velFieldName = name of the finite volume fluid velocity field (default: “U”)

  • voidfractionFieldName = name of the finite volume voidfraction field (default: “voidfraction”)

  • granVelFieldName = name of the finite volume granular velocity field (default: “Us”)

  • ignoreDrag = ignore drag force (default: false)

  • ignoreTorque = ignore torque (default: false)

  • useVoidfractionCorrection = use voidfraction correction, model is selected with switch (available options: voidageFunctionDiFelice, voidageFunctionRong, voidageFunctionTang) (default: true)

  • vpIterMax = maximum number of sub-loops to solve implicit equation. (default: 4)

  • relTolDrag = the sub-loop convergence criterion for drag, with relDeviation=(dragPrev-drag)/drag and convergence is reached if(relDeviation < relTolDrag). If relTolDrag is not set, it is not accounted for. If relTolTorque is also defined, convergence of both criteria must be fulfilled. (default: 1)

  • relTolTorque = the sub-loop convergence criterion for torque, with relDeviation=(torquePrev-torque)/torque and convergence is reached if(relDeviation < relTolTorque). If relTolTorque is not set, it is not accounted for. If relTolDrag is also defined, convergence of both criteria must be fulfilled. (default: 1)

  • CdTorquePrimeDiagonal = diagonal of the torque resistance tensor in body coordinates (default: auto calculated (NOT TESTED! UNDER DEV!))

  • periodicHalo = halos size (by coordinate directions) to restrict domain of influence (based on bounding box) of force calculation. (default: (0 0 0))

  • useVoidfractionCorrection = use voidfraction correction also on torque. (default: false)

This forceModel reads the following forceSubModel switches and overwrites the defaults as indicated in parentheses:

  • scaleDrag

  • scaleDH

  • treatForceExplicit

  • implForceDEM (default: true)

  • verbose

  • interpolation

  • voidageFunctionDiFelice

  • voidageFunctionRong (default: true)

  • voidageFunctionTang

For particleShapeType = "multipshere" and particleShapeType = "convex" the followings switches are read in addition:

  • implTorqueDEM

Examples

particleShapeType multisphere;
forceModels
(
    StokesClumpDrag
);
StokesClumpDragProps
{
    velFieldName "U";
    voidfractionFieldName "voidfraction";
    granVelFieldName "Us";
}

Description

The force model performs the calculation of forces (e.g. fluid-particle interaction forces) acting on each DEM clump (multisphere consisting of several particles). The StokesClumpDrag model calculates the particle based drag force following the approach of Joung 2006, Rheol Acta.

The drag is computed for each sphere of the clump separately where each sphere induces a flow at the position of all other particles of the clump.

For a more detailed discussion of the theoretical foundation, see [1] and [2].

Literature

[1] C. G. Joung. “Dynamic simulation of arbitrarily shaped particles in shear flow”. Rheol Acta 46 (2006): 143–152

[2] M.A. Romero-Valle, C. Goniva, H. Nirschl (2021). “Modeling of non-spherical particle flows: Movement and orientation behavior”. Powder Technology 382 (2021): 351–363

Restrictions

Not valid for sphere particles.

Note

For multispheres consisting of operlapping sphere, this model may become unstable. Construct multispherse with small overlaps – or avoid overlaps entirely!