Bubble necking in a confined channel formed by a pair of elastic plates

Abstract

Bubble dynamics play a crucial role in multiphase flow system. A quick bubble departure process is adorable in processes such as gas evolution and boiling heat transfer. Bubble necking is beneficial for high gas production efficiency. However, the formation of bubble necking depends on the balance between surface tension force and buoyancy force, i.e. it is mostly limited to the flow characteristics. Here, a novel method using a pair of elastic plates (made of Polyethylene terephthalate (PET)) which promotes the bubble necking and departure in confined space by oscillation of plates is investigated experimentally based on Particle Image Velocimetry (PIV). The velocity of bubble and liquid throughout the process within elastic plates (the thickness of 0.05 mm and the length of 12 mm) are about 5 and 35 times higher than that within rigid plates (the thickness of 0.5 mm and the same length). Plate dynamics with different rigidities coupling bubble dynamics are also investigated in detail. The surface tension force for bubble between elastic plates is lowered due to the changed shape during the expansion process of elastic plates caused by bubble growth. The radius of bubble necking versus breaking time is found fitted with the power function line as r∼τα (α varies in the range 0.82–0.85). It is found that the bubble necking rate increased with the length of the plate due to the flow effect caused by the oscillation of plates. Our study reveals that elastic plates benefit bubble departure and liquid replenishment for cases in confined space, showing their potential applications in microfluidic system.