Development of a granular normal contact force model based on a non-Newtonian liquid filled dashpot

Normal contact force models often suffer from a weak prediction of collisions between particles. They regularly fail to predict an adequate energy restitution behavior with increasing normal impact velocity. In particular, most non-linear models predict a net attraction force between two impacting particles near the end of a collision, which is unrealistic according to reported results. Such limitations have provided the impetus for the development of a normal contact force model that better predicts the unfolding of a collision between two particles. This model comprises a Hertz elastic force and a dissipative force that is evaluated by the motion of a non-Newtonian liquid in a dashpot. The model parameters are set using experimental restitution data for particle/particle and particle/wall contacts. In the current work, the measurement of energy restitution for particle/wall collision was carried out using several materials over a wide range of impact velocities, whereas particle/particle collision data were obtained from the literature. Model predictions for microscopic (e.g. particle velocity) and macroscopic (e.g. collision time) quantities are presented and compared with those from other non-linear models and experimental data. The model is observed to adequately predict the coefficient of restitution and to decrease the attraction force at the end of a collision.

A normal contact force model is developed to simulate the collision of two particles. This figure shows that the values of the coefficient of restitution predicted by this model (lines) when the impact velocity varies are in good agreement with experimental data (symbols) for a wide range of materials.Figure optionsDownload as PowerPoint slideHighlights
► A normal contact force model is proposed to simulate the collision of two particles.
► The model is more accurate than other models from the literature.
► The model does not exhibit a spurious attractive force at the end of the collisions.
► The coefficient of restitution increases with the impact velocity for soft materials.