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.