The group, led by Professor Michael P. Brenner, investigated how air bubbles interact with solid particles in a fluid, specifically in sand. Traditionally, it was assumed that air bubbles would move toward the surface of the fluid, regardless of the presence of solid particles.
However, the Caltech engineers discovered that, under certain circumstances, air bubbles can become trapped in sand and then be transported in the opposite direction—upward. This phenomenon occurs when the fluid is highly viscous and the solid particles are small and spherical.
To demonstrate this effect, the engineers conducted experiments using a water-glycerol mixture and glass beads as the solid particles. They observed that when air bubbles were introduced into the mixture, they became trapped in the glass beads and were transported upward by the flow of the fluid.
This discovery has important implications for industries such as agriculture and oil drilling. In agriculture, it could be used to improve irrigation systems by ensuring that water and nutrients are evenly distributed throughout the soil. In oil drilling, it could be used to improve the efficiency of oil extraction by preventing the accumulation of air bubbles in the oil reservoirs.
The Caltech engineers' findings have been published in the journal "Physical Review Letters."
