Microbubbles coalescence

SIZE DISTRIBUTION OF SYNTHETIC MICROBUBBLES FORMATION, COALESCENCE, FISSION, AND DISAPPEARANCE... 

Apparent reversible and/or cyclical behavior Microbubble formation and coalescence versus microbubble fission and disappearance... 

In the final series of measurements, a prolonged effort was made to record the cyclical process of microbubble forma-tion/coalescence/fission/disappearance in considerable detail. The... 

In conclusion, it is possible to prepare concentrated gas-inwater emulsions using various surfactant mixtures. The artificial, surfactant-stabilized microbubbles produced apparently undergo a cyclical process of microbubble formation/coalescence/fission/dis-appearance, where the end of each cycle is characterized by a collapse of the gas microbubbles into large micellar structures — only to re-emerge soon after as newly formed, gas microbubbles. This cyclical microbubble process is promoted by prior mechanical agitation of, and hence entrapment of macroscopic gas bubbles in, these saturated surfactant solutions. 

Bubbles in microbubble colunuis are observed to be separated by a liquid film from the wall at almost all gas space velocities. At low gas space velocities, the microbubble column experiences bubbly flow. The bubbly flow is defined by microbubbles, which are spherical and as large as the channel diameter. Since bubbles of this size are highly unstable without surfactants, the gas space velocity has to be low enough to allow enough space between bubbles in order to prevent coalescing. 

The term emulsion refers to a mixture of two non-miscible liquids, one of which is dispersed within the other in the form of droplets. Foam is a mixture of microbubbles in a liquid. The physico-chemical properties of the products are important for stabilizing emulsions and foams. If the emulsion is not stabilized, the droplets coalesce when the stirring ceases and the emulsion gradually subsides. It is the function of the egg yolk to stabilize the mayonnaise. Anyone who ever prepared a mayonnaise or whisked egg whites will have understood that the beater is a precious utensil for achieving an emulsion or a foam/mousse. It is for this reason that we discuss this issue here. 

Nanobubbles and microbubbles can be generated from a porous nozzle as long as the nozzle is wetted by the liquid and the gas flow rate is low. A bubble growing at the exit of one of the pores of a poorly wetted porous nozzle coalesces with bubbles growing at the exits of pores located around it. As a result, only large bubbles equivalent to the diameter of the porous nozzle are successively generated from the poorly wetted porous nozzle. 

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