Interaction between gas channels in water-saturated sands

This work investigates the interaction between gas channels in a vertical Hele-Shaw cell when air is injected simultaneously from two points at a constant flow rate. Unlike single-injection experiments, this dual-point system induces the formation of numerous bubbles, thereby intensifying the interactions between air channels. We use an image analysis technique for tracking motion in the granular bed to define a flow density parameter throughout the cell. The vertical accumulation of this parameter ($n_z$) reveals two specific heights, one marking a finger-to-fracture transition and another indicating the average interaction height of the air channels. Conversely, its horizontal accumulation ($n_x$) assesses the extent of overlap in the fluidized zones created by each airflow. Notably, the analysis indicates that the optimum distribution of the three phases in the system is more closely related to the interaction's variability than its intensity. This finding is significant for industrial applications such as air sparging and catalytic reactors.