Bubble Formation Due to a Submerged Capillary Tube in Quiescent and Coflowing Streams

Abstract

The case of bubble formation in both quiescent and moving streams due to the injection of a constant gas flow through a small tube is considered. Relationships predicting the expected size and quantity of bubbles generated are proposed. These are compared with measurements taken with stream velocities up to 9 ft/sec, while generating gas bubbles from 40 to 700 microns in diameter. For the case of generation in a quiescent stream the forces due to the virtual mass, surface tension, viscous drag, buoyancy, and the wake formed by the preceding bubble are accounted for. There still remains some question (only partly answered by a comparison with measurements) as to the proper added mass coefficient and the geometry of the bubble previous to detachment, as well as an adequate estimate of the interaction with a preceding bubble’s wake. The proposed model for generation in a moving stream is in good agreement with actual measurements for co-flowing velocities between 1 and 9 fps and capillary tubes in the order of 10−3 cm in dia.

Bubbling in a co-flow at high Reynolds numbers

“…Although nanobubbles can be generated through porous membranes injecting the gas at a pressure of the order of 10 MPa, 26 a common way to reduce the bubble size is to inject the gas stream within a liquid co-flow. 27 This technique also avoids the coalescence of bubbles and it is nowadays extensively employed in microfluid applications. 28 An example can be found in the large number of micro devices based on the so-called flow-focusing configuration, where an inner gas stream, surrounded by an outer liquid co-flow, is driven through a small orifice.…”

“…More importantly regarding the present context, they also considered the possibility of including a liquid co-flow surrounding the forming bubble. From the experimental point of view, Sevilla et al, 23 and latter on Gañán et al, 38 performed a series of experiments using the co-flowing geometry previously analyzed by Chuang and Goldschmidt 27 and Oguz and Prosperetti 19 with the aim at determining the formation mechanisms and scaling laws of air bubbles inside a laminar, high-Reynolds-number water jet discharging in a still air atmosphere. In this work, the authors identify two different regimes, namely a jetting regime and a bubbling regime, depending on the Weber number and the gas-to-liquid velocity ratio.…”

Theoretical Analysis of Bubble Formation in a Co-Flowing Liquid.

“…Bubble formation in co-flowing or counter-flowing liquids under constant gas flow conditions has been investigated both experimentally and theoretically (Chuang and Goldschmidt, 1970;Sada et al, 1978;Takahashi et al, 1980;Räbiger and Vogelpohl, 1982;Fawkner et al, 1990;Oguz and Prosperetti, 1993). Several spherical, pseudo-spherical and non-spherical models have been reported for bubble formation in flowing liquids.…”

Microbubble movement during its formation in a co-flowing liquid in a microfluidic chip

“…Both spherical and non-spherical theoretical models have been proposed to describe the formation process of single bubble, including one-stage models [2][3][4], double stage models [5,6], multi-stage models [7] and non-spherical models [8][9][10]. Meanwhile, experiments were performed by Liu [4], Takahashi [11], Yu [7], Koichi Terasaka [8], Najafi [9] and Bhunia [5] to investigate the phenomena of bubble formation in quiescent and flowing liquid.…”