Energy transfer and dynamic response of a gasbag-driven confined granular bed

When gasbag inflation is used to drive a granular bed in a confined space, the system exhibits strong nonlinearity arising from membrane deformation, particle contact, and boundary constraint. This study investigates the dynamic response and energy-transfer characteristics of a gasbag-driven confined granular bed through experiments and DEM-FEM simulations. The dispersal patterns and particle velocity distributions were recorded under different driving pressures, and a parametric numerical model was used to examine the effects of driving pressure and particle diameter. The results show that, within the tested pressure range of 0.2-3.0 MPa, the characteristic particle velocity follows an approximately pressure-dependent increasing trend, indicating effective conversion of pressure loading into particle kinetic energy. However, as the particle diameter increases, the particle velocity decreases nonlinearly after a critical size range despite the reduction in total particle mass. This behavior is associated with enhanced particle-particle contacts, stronger particle-wall interaction, and possible Janssen-type stress redistribution in the confined bed. Therefore, the dominant response may shift from inertia-dominated dispersion to contact-constrained motion with increased wall friction.