Rising behavior of air bubbles in superposed liquid layers

Abstract

An air bubble that passes through a horizontal interface from a lower layer of Freon‐113 to an upper layer of aqueous glycerol forms a two‐phase bubble in the upper layer as a result of entrainment of a certain volume of Freon‐113 from the lower layer. The volume of entrained Freon‐113 and the rise velocity of such a two‐phase bubble have been measured. The former increases with an increase of the bubble size irrespective of the viscosity of the upper liquid. The latter is somewhat lower than that of a normal air bubble of the same size.

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

“…According to Selecki and Gradon (1972) the critical radius ricr is given by where d i ) denotes the surface tension of phase i and p(i) the mass density. If the lower liquid (1) is Freon 113 ( p @ ) = 1.58 g/cm3, dl) = 19 dyn/cm) and liquid two isa98.8 yo aqueous glycerol solution (p(2) = 1.26 g/cm3, d 2 ) = 64 dyn/cm), (1 .l) predicts ricr = 2.20 mm, quite close to the experimentally determined critical radius of 1.70 mm (Mori et al 1977; see also table 1, system 6B). I n addition Selecki & Gradon (1972) conclude that bubbles exceeding that size always have to form multiple drops ; and the observation of Mori et al (1977) that the rise velocity is lower than that of a (single) air bubble but larger than that of a rigid sphere seems to substantiate that claim.…”

“…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.…”

“…Both Mercier et al (1972) and Mori et al (1977) observed that the lower liquid encapsulated the air bubble quite non-uniformly, especially for the larger-size bubbles. Studying these configurations may indeed require ' spherical-cap ' studies, like the ones introduced by Johnson & Sadhal (1983).…”

On the thermocapillary motion of partially engulfed compound drops

“…No experiments concerning the thermocapillary motion of partially engulfed drops are available so far. We believe that the motion in the direction of temperature gradient can be observed for the compound drops used previously in the experiments by Mercier et al (1974), Mori et al (1977), Mori (1978) and Hashimoto & Kawano (1990) adapting the classical experimental technique of Young et al (1959). Observation of the motion in the direction opposite to that of the temperature gradient might be a more complicated task, since this phenomenon takes place when the inner interface is substantially more thermocapillary active than the outer ones, i.e.…”

“…A simple method to form liquid-gas compound drops is to let air bubbles rise from one liquid into another one above it. The motion of an air bubble rising through a liquid and crossing a plane interface into another immiscible liquid of lower density has been experimentally studied by Mercier et al (1974), Mori et al (1977), Mori (1978) and Hashimoto & Kawano (1990). With distilled water as the lower layer and lighter oil as the upper, it was found by Mercier et al (1974) that the water attaches onto the bubble as it passes upward into the oil.…”