(270d) Development of an Accurate Granular Normal Contact Force Model Based On a Non-Newtonian Liquid Filled Dashpot

It is well known that normal contact force models from the literature may fail to predict adequately particle collisions. For instance, they regularly predict inaccurately the energy restitution behavior when the normal impact velocity is increased. For example, most non-linear models yield a non-zero attractive force between two impacting particles just before they break apart, which is unrealistic. Such limitations have motivated the development of a novel normal contact force model that better predicts the unfolding of a collision between two particles. This model brings into play a Hertz elastic force and a dissipative force the value of which depends on 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 this work, the measurement of energy restitution for particle/wall collision was done using several materials for a wide range of impact velocities, whereas particle/particle collision data were taken from the literature. Model predictions for microscopic (e.g. particle velocity) and macroscopic (e.g. collision time) quantities will be presented and compared to experimental data and results obtained from other non-linear models. It will be shown that the model adequately predicts the coefficient of restitution and that it yields a much smaller attractive force at the end of a particle collision.