IBClogging

Syntax

Defined in couplingProperties dictionary.

meshMotionModel IBClogging;
IBCloggingProps
{
    alpha                scalar;
    volumefractionScale  scalar;
    UpThresh             scalar;
    keepOnceFrozen       Switch;
    voidfractionFieldName "voidfraction";
    UsFieldName          "Us";
}

  • alpha : relaxation parameter in the range [0; 1]. This parameter determines blending between current force field and the force field required to force the fluid into motion with the geometry. This parameter may severly affect stability. (default: 0.5)

  • volumefractionScale : scale local particle volume fraction by this factor for criterion to block a cell. (default: 10)

  • UpThresh : upper threshold for particle cell velocity to block a cell, i.e. the cell is only blocked if the (cell-mapped) particle velocity is smaller than this value. (default: 0.001)

  • keepOnceFrozen : evaluate blocking criterion every coupling step (false) or keep a cell blocked forever if blocking was invoked once (true). (default: true)

    Note

    Blocked cells are not stored beyond the end of a simulation and will be re-built from current particle data after resuming a simulation.

  • voidfractionFieldName : name for voidfraction field used in particle volume fraction criterion (default: “voidfraction”)

  • UsFieldName : name for particle velocity field used in particle velocity criterion (default: “Us”)

Examples

meshMotionModel IBClogging;
IBCloggingProps
{
    alpha 0.1;
    volumefractionScale 1e4;
    UpThresh 0.01;
}

Description

The IBClogging-model blocks cells using the Immersed Boundary Method based on two particle criteria:

  1. if volumefraction * volumefractionScale > 1 and

  2. if the particle velocity Us < UpThresh

If both conditions are true, then a cell is blocked (field body = 1), all its neighbouring cells are half blocked as a halo (field body = 0.5) and this model will create a body force on these cells which counteracts the flow and decreases it towards zero. The intensity of the forcing can be controlled by the model parameter alpha.

Note

The value of alpha will affect stability.

Note

It might be useful do increase the dragforce in regions with body > 0 using the scaleDragByFieldFunction forceSubModel.

Restrictions

  1. Halo cells are not recognized across processor boundaries.

  2. keepOnceFrozen = true will not work for restart of simulations, meaning that old frozen cells will be forgotten and re-built again from current particle data when re-starting from a simulation snapshot.