The terminal rise velocity of 10–100 μm diameter bubbles in water

Single bubbles of very pure N2, He, air and CO2 were formed in a quiescent environment in ultra-clean water, with diameters ranging from 10 to 100 μm. Their terminal rise velocities were measured by high-speed video microscopy. For N2, He and air, excellent agreement with the Hadamard–Rybczynski (H–R) equation was observed, indicating that slip was occurring at the liquid–vapor interface. For CO2 bubbles with diameters less than 60 μm, the terminal rise velocities exceeded those predicted by the H–R equation. This effect was ascribed to the enhanced solubility of CO2 compared with the other gases examined. The presence of a diffusion boundary layer may be responsible for the increased terminal velocity of very small CO2 bubbles.

The rise velocity of air, N2, He, and CO2 bubbles in pure water are compared with Stokes' law (—) and Hadamard–Rybczynski (- - -) predictions. A mobile bubble surface is implied.Figure optionsDownload as PowerPoint slide