Bubbles rising through a layer of Carbopol capped with water

Abstract

Air bubbles are injected into a Carbopol column capped with water to mimic ebullition from lake sediments. The first bubble sets an invisible path as it rises through the Carbopol. Subsequent bubbles rise along this path and, unlike the first bubble, break up into two separate bubbles. The leading bubble rises through the water column, while the smaller breakup bubble separates and remains trapped within the Carbopol. A conduit that forms above this breakup bubble gradually fills with water from the upper layer. After a period of growth this conduit reaches an equilibrium depth, and then starts to shrink. Inside the conduit, the rising bubbles resemble Taylor bubbles, but have velocities approximately 5–7 times the maximum velocity of standard Taylor bubbles. The variation in rise velocity depends on the interaction of the rising bubble with previous breakup bubbles. In addition, rising bubbles expel water from the conduit and water flows back after bubbles escape. This process can enhance the transport of heat and contaminants to and from aquatic sediments during ebullition events. • A damaged pathway forms inside Carbopol due to the passage of bubbles. • Bubbles break up as they cross the Carbopol–water interface. • Upper portion of the damaged pathway evolves into a water-filled conduit. • Bubbles rise much faster inside the conduit than standard Taylor bubbles. • Water flows in and out of the conduit, enhancing mixing in aquatic sediments.