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Abstract

The rate of growth of bubbles forming on a wall from a liquid initially uniformly supersaturated with a dissolved gas was investigated. Attention was directed to the effect of the contact angle.

Theoretical predictions for the growth rate of a spherical bubble tangent to a wall were carried out with a digital computer. The predictions included the diffusion equation and the continuity equation. The energy equation was neglected; viscosity and surface tension were assumed nil. The results are compared with existing predictions for a 90-deg. contact angle. For extremely slow growth, the theoretical growth coefficient is about 30% smaller for a bubble with zero contact angle compared to one with a 90-deg. contact angle. For fast growth the difference is much less.

Experimental growth rates were determined photographically for bubbles of carbon dioxide coming out of solution from water at an artifical nucleation site. Different contact angles from 15 to 89 deg. were obtained by coating the wall with various nonwetting agents. Every bubble showed changes in its contact angle during growth. No effect of contact angle on the growth rate could be detected.