Influence of Enveloping Water Layer on the Rise of Air Bubbles in Newtonian Fluids

Abstract

The rise of air bubbles in five Newtonian fluids is compared for two different cases of bubble formation and release: (a) directly into the five homogeneous fluids and (b) directly into a layer of distilled water underlying each one of the five liquids. It was found in Case (b) that medium-sized bubbles rise steadily through the upper liquid with an enveloping water layer of variable thickness. The influence of this water layer on the trajectory, shape, and terminal velocity of bubbles is particularly significant in low viscosity upper phases. The resulting water mass transfer per bubble through the lower density upper phase depends on viscosity and was markedly greater for the higher viscosity fluids. The behavior and the nature of the detachment of the water layers from the larger size bubbles are also presented and discussed.

On the deformation and drag of a type-A multiple drop at low Reynolds number

“…In this paper we have studied the hydrodynamic behaviour of a type-A double emulsion droplet in the low-Reynolds-number region. For droplets generated in a diffusion column, differences from single-droplet behaviour do not seem to show up until the droplets are sufficiently large (Mercier et al 1974;Mori et al 1977). This implies that not all of the three Reynolds numbers involved are small.…”

“…Roden critical size the first differences were found, and the terminal rise velocity through the continuous phase two was less than that of the single bubble but larger than for a rigid sphere (of the bubble density) rising through the oil. As a matter of fact, for the most viscous oil used (kinematic viscosity d2) = 0.55 cmz/s) the rigid-sphere limit was almost reached (see figure 3 of Mercier et al 1974). Using the data supplied, we thus see that in this case no difference from the behaviour of single bubbles was found unless the Reynolds number of region i (based on bubble radius) exceeded the values 194.7, 3.5 and 13 in regions one, two and three respectively (three is the inside or bubble region).…”

“…Dispersed droplets or bubbles rise through the heavier liquid. A multiple droplet is formed when the single droplet breaks through the previously plane onetwo interface (Li & Asher 1973;Mercier et al 1974).…”

“…For gas bubbles rising through water and then through mineral oils (as the lower (1) and upper (2) liquid respectively) marked differences in shape, trajectory and rise velocity between the two-phase air-water bubble and normal air bubbles in the same oil have been found (Mercier et al 1974). Since, in that case, the lower liquid (1) has the higher surface tension, all gas bubbles will cross the onetwo interphase.…”

Growth and translation of a liquid-vapour compound drop in a second liquid. Part 1. Fluid mechanics

“…There have been numerous theoretical as well as experimental studies in this area. For example, ; Sideman, Hirsch & Gat (1965) ; Sideman & Gat (1966) ; Mercier et al (1974) mentally studied the fluid mechanics associated with such drops. However, little progress had been made in terms of the theoretical fluid mechanics until recently.…”