rolling_friction model cdt

Purpose

A very basic rolling friction model

Syntax

rolling_friction cdt [other model_type/model_name pairs as described here ] settings keyword values

zero or one keyword/value pair may be appended after the keyword settings (after all models are specified)

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

Associated material properties

Material interaction properties

coefficientRollingFriction ( $\mu_r$ ): Coefficient of rolling friction [–]

Description

This model can be used in the rolling_friction argument of both particle_contact_model and wall_contact_model.

The constant directional torque (CDT) model adds the following torque contribution $M_r$ [Nm] to the angular momentum equation:

$M_{r} = \mu_r k_n \delta_n \frac{\omega_{\text{shear}}}{\|\omega_{\text{shear}}\|} r^*,$

where $\omega_{\text{shear}}$ [radians/s] is the projection of $\omega_r = \omega_i - \omega_j$ into the shear plane, $\omega_i$ and $\omega_i$ are the angular velocity vectors of particles i and j, respectively, $k_n$ [N/m] is the normal spring stiffness obtained from the normal contact law, $\delta_n$ [m] is the the normal overlap, $r^*$ [m] is the effective radius (see here) and $\| . \|$ indicates the Euclidean norm of a vector.

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 friction torque.

Coarse-graining information:

Using coarsegraining in combination with this command might lead to different dynamics or system state and thus to inconsistencies.

Default

torsionTorque = ‘off’

References

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