Diffusive growth and compressibility of bubbles in porous media

Kam, S.I. and Rossen, W.R., Proc. EuroConference on Foams, Emulsions and Applications, Delft, The Netherlands, 5-8 June 2000.

 Abstract

Within the slurry at the bottom of waste tanks at the Hanford Nuclear Reservation in the U.S., bubbles slowly grow by diffusion from the surrounding liquid. The compressibility of these bubbles is a crucial factor in monitoring these tanks, because one can quantify the accumulation of these potentially dangerous gases from the movement of the liquid level in the tank with barometric pressure, if one knows the compressibility of the gas.

We present a model for the growth of bubbles in a porous medium and for the compressibility of these bubbles subjected to a sudden change in pressure. If capillary forces are strong, they can affect the diffusive mass flux to individual bubbles and distort the distribution of bubbles over time, altering the effective compressibility of the population of bubbles. Predicted differences between effective compressibility with increasing and decreasing barometric pressure matches data on changes of liquid level in the Hanford tanks with varying barometric pressure.