fix couple/cfd/recurrence command

Syntax

fix ID group-ID couple/cfd/recurrence keyword values

  • ID, group-ID are documented in fix command

  • couple/cfd/recurrence = style name of this fix command

  • zero or more keyword/value pairs may be appended

  • keyword = transfer_density or transfer_type or transfer_force or transfer_fluctuations or transfer_tracer or limit_fluctuations or max_vfluc or limit_convection or max_vconv or relative_limit or remove_vel_across_walls or region

    transfer_* values = yes or no
    limit_fluctuations value = yes or no
    max_vfluc value = maximum fluctuation velocity
    limit_convection value = yes or no
    max_vconv value = maximum convection velocity
    relative_limit value = yes or no
    remove_vel_across_walls values = name of fix gran/walls and absolute value of critical force
    region value = name of region

Examples

fix cfd2 all couple/cfd/recurrence transfer_force yes transfer_fluctuations yes

fix cfd3 all couple/cfd/recurrence transfer_force yes transfer_fluctuations yes limit_fluctuations yes max_vfluc 0.05 relative_limit no region closeToWall

Description

This fix exchanges the recurrence CFD relevant data between LIGGGHTS and CFDEMcoupling. Particle positions, velocities, radii and volumeweights are transferred from LIGGGHTS to CFDEMcoupling, the recurrence-prescribed velocities from CFDEMcoupling to LIGGGHTS.

If needed, particle types and densities can also be communicated from LIGGGHTS to CFDEMcoupling (disabled per default) and forces (e.g. drag), velocity fluctuations and tracer concentrations from CFDEMcoupling to LIGGGHTS (disabled per default). Fluctuations or convection velocity (or both) may be limited with an absolute or relative (in units of particle radius per time step) value, either everywhere or in a specific region.

If remove_vel_across_walls is enabled by providing the name of the gran/wall fix, it is checked for each particle if it is subject to a wall contact force. If so, the velocity component in the direction towards the wall is reversed such that the particle does not try to cross the wall. The value of the critical force provided by the user determines at which point the fix gets active for each particle.

This fix needs a fix couple/cfd before it is defined.