A comparison of pendulum experiments and discrete-element simulations of oblique collisions of wet spheres

Oblique collisions of two spherical particles coated with a thin layer of viscous liquid are considered. Experimental measurements are performed using particle tracking velocimetry. Comprehensive experimental data for collisions with an impact angle between 0° - 60° are presented. Collisions are characterised by the Stokes’ number, the coefficient of restitution, and the rotational velocity. The experiments are compared to numerical simulations using the discrete element method (DEM). The translational velocities predicted by the simulations were in good agreement with the experiments at high Stokes’ number, where the models are dominated by the normal components. As the tangential forces become more significant (i.e. at low to medium Stokes’ number, and high collision angle), agreement between the simulations and experiments is poorer. At low Stokes’ number the translational velocities were in good agreement with the experiments, but was poorer at high Stokes’ number.