Date of Award

5-2001

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Computer Engineering

Advisor

Edward V. Thompson

Second Committee Member

François G. Amar

Third Committee Member

Douglas W. Bousfield

Abstract

The growth characteristics of gas bubbles in supersaturated liquid solutions were measured in preliminary experiments involving glass bottles followed by more controlled and systematic investigations using a custom designed experimental apparatus. It was proven that the presence of pre-existing gas was responsible for the bubble formation observed. Bubble growth occurred in very regular cyclical patterns at specific locations containing trapped gases. In the custom designed apparatus, liquids could be saturated with gases and supersaturated solutions made by depressurizing the system. Artificial capillaries, pre-seeded with air bubbles, behaved in a similar manner to naturally occurring sites containing pre-existing gases. The apparent gap in time between the detachment of one bubble and the first observable appearance of the next bubble, denoted by earlier researchers as a “nucleation” lapse time, was identified as a misnomer. Further analysis focused on measuring bubble growth times, or the time between consecutive detachments. The long term behavior of a series of air bubbles in supersaturated water, growing from artificial capillaries positioned inside the apparatus, revealed that bubble detachment diameter changes very little from bubble to bubble, but that the bubble growth times tend to increase as the dissolved gas concentration decreases. In further experiments, the bubble growth characteristics of the first full bubble only were analyzed. Air in water experiments involving three capillary sizes, an altered saturation routine, and a partial depressurization were conducted along with experiments using carbon dioxide in water and helium in water. Neither the bubble growth model proposed by Manley (1960), which assumed a diffusion-only type solution, nor the theory of Scriven (1959), which accounted for both diffusion and convection, accurately predicts the bubble growth times observed, particularly at higher supersaturation ratios (> 25). Manley predictions are as much as 1500% too high while Scriven predictions are as much as 400% too high at the higher supersaturation ratios. A new model, based on the Scriven theory, reformulates the bubble surface velocity term and includes an additional restriction on one of the boundary conditions. Bubble growth time predictions from the new model at the higher supersaturations were always within 25% of the experimentally measured value.

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