virtualMassForce

Syntax

Defined in couplingProperties dictionary.

forceModels
(
    virtualMassForce
);
virtualMassForceProps
{
    velFieldName          "U";
    phiFieldName          "phi";
    splitUrelCalculation  false;
    Cadd                  0.5;
    UInterpolationType    "cellPointFace";
    DDtUInterpolationType "cellPointFace";

    // (optional) forceSubModel switches
    treatForceExplicit    switch;
    treatForceDEM         switch;
    interpolation         switch;
};

  • U = name of the finite volume fluid velocity field. (default: U)

  • phi = name of the finite volume flux field (default: phi)

  • splitUrelCalculation = indicator to split calculation of Urel between CFDEM and Aspherix (default: false)

  • Cadd = scalar value for virtual mass coefficient. (default: 0.5)

  • UInterpolationType = interpolation type for U field. (default: cellPointFace)

  • DDtUInterpolationType = interpolation type for ddt(U) field. (default: cellPointFace)

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

  • scaleDrag

  • scaleDH

  • treatForceExplicit (default: true)

  • treatForceDEM

  • interpolation

Examples

forceModels
(
    virtualMassForce
);
virtualMassForceProps
{
    Cadd         0.5;
}

Description

Calculates the virtual mass force for each particle, i.e. the force due to the additional inertia of surrounding fluid:

\vec{F}_\mathrm{virt} = C_\mathrm{add} \rho V \frac{\partial \vec{u}_\mathrm{rel}}{\partial t}

with C_\mathrm{add} being set by the keyword Cadd.

This term may be neglected in case of low ratios of fluid to particle density but is crucial in the adverse scenario, for instance when simulating gas bubbles in liquid.

This model should be used in combination with the corresponding setting on the DEM side, i.e. using the add_fluid_mass setting in the enable_cfd_coupling command, which increases the particle inertia during integration.

Note

Especially for setups involving fluid flow without momentum sources aside from particle motion and disperse partciles, increasing the particle inertia using the add_fluid_mass setting in the enable_cfd_coupling command and neglecting the additional virtual mass force computed by this model yields good results.

Restrictions

This model is not fully validated. This model requires setting splitUrelCalculation true.