Unveiling self-propelled ascent in granular media

Abstract

This study investigates the self-propelled ascent of cylindrical vibrators in granular media under varying force amplitudes, frequencies, particle sizes, and rotational motions. By integrating experimental observations with numerical simulations, critical yielding and shear flow mechanisms are identified, revealing how these processes facilitate vibrator ascent. The results indicate that force amplitude, in conjunction with vibrator rotation, is crucial for overcoming granular confinement. Rotational motion promotes vortex formation and shear banding, thereby reducing resistance and enhancing void-filling beneath the vibrator. A key contribution is the introduction of a characteristic length scale for quantifying dynamic heterogeneity, which enables a predictive framework for determining the critical force required for ascent. Further findings demonstrate that smaller particles, lower frequencies, and higher force amplitudes accelerate ascent, while also uncovering a novel interplay between particle settling and excitation frequency. Finally, a predictive model linking excitation conditions to ascent velocity is proposed, providing a transformative approach for optimizing granular systems in engineering and robotics applications.