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:link(liws,http://www.cfdem.com)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

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gran rolling_friction cdt model :h3

[Syntax:]

rolling_friction cdt \[other model_type/model_name pairs as described "here"_pair_gran.html \] keyword values :pre
zero or more keyword/value pairs may be appended to the end (after all models are specified) :l
  {torsionTorque} values = 'on' or 'off'
    on = also the normal, relative rotation (torsion) contributes to the resulting torque
    off = only the tangential, relative rotation contributes to the resulting torque :pre

[Description:]

This model can be used as part of "pair gran"_pair_gran.html and
"fix wall/gran"_fix_wall_gran.html

The constant directional torque (CDT) model adds an additional torque
contribution, equal to

torque_rf = rmu*k_n*delta_n*w_r_shear/mag(w_r_shear)*(R*).

w_r_shear is the projection of w_r into the shear plane, where w_r = w1-w2

If the rolling friction model is activated, the coefficient of rolling friction (rmu) must be defined as

fix id all property/global coefficientRollingFriction peratomtypepair n_atomtypes value_11 value_12 .. value_21 value_22 .. .
    (value_ij=value for the coefficient of rolling friction between atom type i and j; n_atomtypes is the number of atom types you want to use in your simulation) :pre

IMPORTANT NOTE: You have to use atom styles beginning from 1, e.g. 1,2,3,...

[Torque information:]

By default the relative, normal rotation (torsion) is subtracted and does not contribute to the resulting torque. By setting the {torsionTorque} keyword to 'on', the full relative rotation contributes to the rolling friciton torque.

[Coarse-graining information:]

Using "coarsegraining"_coarsegraining.html in
combination with this command might lead to
different dynamics or system state and thus to 
inconsistancies.

NOTE: "Coarsegraining"_coarsegraining.html may or 
may not be available in LIGGGHTS(R)-PUBLIC.

[Default:]

{torsionTorque} = 'off'

[(Ai)] Jun Ai, Jian-Fei Chen, J. Michael Rotter, Jin Y. Ooi, Powder Technology, 206 (3), p 269-282 (2011).
