Experimental study of airlift transport and pressure response of cylindrical cores regulated by gas–liquid flow structures

Airlift reverse-circulation coring transports cylindrical cores by injecting gas into a riser. Near-pipe-diameter cores are wall-confined, making their motion sensitive to gas–liquid structures. A visualized airlift core-transport system was used to examine the coupling among gas–liquid structures, pressure response, and core motion through high-speed imaging, multi-point pressure measurements, and an instrumented core. Increasing gas injection drove the flow from bubbly flow to large-scale intermittent structures. Correspondingly, the pressure response shifted from high-frequency, low-amplitude disturbances to low-frequency, high-amplitude pulsations. Core introduction increased near-field pressure-fluctuation amplitude, with limited changes in characteristic pressure frequency. Instrumented-core measurements showed larger attitude and axial-acceleration fluctuations during airlift transport than during hydraulic single-phase transport, consistent with intermittent core support. The pressure-inferred recurrence length mapped the pressure-fluctuation timescale to a spatial recurrence scale based on gas-phase convection. Mean core transport velocity was positively associated with the in situ gas velocity estimated using two drift-flux correlations, giving through-origin slopes of 0.3185 and 0.3368. Model selection changed the fitted coefficient but did not alter the observed velocity association. The cycle-scale ratio of core displacement to recurrence length was approximately one third and is interpreted as a kinematic transport scaling rather than an independent causal correlation. These results show that intermittent gas–liquid structure dynamics are essential for characterizing airlift core transport beyond the mean liquid velocity alone. Within the tested air–water laboratory conditions, the results provide local-scale guidance for interpreting pressure response and core transport in airlift reverse-circulation systems.