The drag on a vibrated intruder moving in the confined granular media

Drag on a circular intruder traversing a shape-heterogeneous granular mixture

The main aim of our work is to explore the effect of particle shape heterogeneity on the dynamics of an intruder moving through a two-dimensional mixture of dumbbells and disks. In spite of similar physical conditions (the mass of the dumbbell is the same as that of the disk) and the same area fraction, we noticed a significant difference in the drag experienced by the intruder as the mixture concentration varies. The propagation of stress from the intruder to the granular grains manifests in the form of force chains, and interestingly these force chains can vary significantly depending on the shape of the grains. These differences, however, appear to be suppressed in the frictionless case where the force chains cannot extend very far from the initial point of contact. Apart from particle shape, the effect of the area fraction of the system and the size of the intruder have also been explored. As the area fraction increases, the drag force on the intruder increases owing to the increase in the contact forces. Finally, we present the velocity and stress fields at different dumbbell fractions and for various intruder diameters to show the effect of the moving intruder on its surrounding particles.

Dynamical behaviors of self-propulsion intruder buried in granular materials

Self-propulsion intruder motion in particles is common in the field of biomimetic and exploration instrument development. In this paper, numerical simulations and laboratory experiments are conducted for the spiral upward phenomenal motion of self-propulsion spherical intruder in granular media. Dynamic particle buoyancy and particle Saffman lift are proposed to establish a dynamic model of the intruder under horizontal simple harmonic excitations. The dependencies of the net particle lift force on the horizontal displacement and the local fluidization parameters of granular are discussed. The results show that horizontal displacement of the intruder and the coordination number of particles are jointly determined by the excitation amplitude and frequency, and the intruder starts to rise when they simultaneously reach the critical value. The dynamic particle buoyancy and particle Saffman lift have clarified the ascent mechanics. Meanwhile, the motion trajectory of intruder in space is inverted conical spiral, and the vibration causes the gap filling effect after the local particle fluidization is the mechanism of the intruder floating up motion.