Faster Taylor bubbles

Gas volumes with an equivalent spherical diameter greater than that of the tube in which they rise by buoyancy - so-called Taylor bubbles - assume a characteristic bullet shape and ascend with a velocity that is dependent primarily on the tube diameter, and also on the physical properties of the liquid, but, remarkably, is mostly independent of the gas volume. The requirement of liquid volume conservation suggests a plausible explanation of this paradoxical feature in that the space vacated under the rising bubble must be replenished by the liquid film falling along the bubble surface. It is demonstrated by numerical means that, by limiting the bubble diameter, a cylindrical 'cage' of thin vertical rods coaxial with the tube permits the flow rate of this film to increase, with the result that the bubble is able to ascend with a significantly higher velocity than in an empty tube with the same diameter.

Automated summary

Taylor bubbles, gas volumes with a diameter larger than the tube in which they rise, exhibit a characteristic bullet shape and ascend at a speed primarily determined by the tube diameter and liquid properties. By limiting the bubble diameter and using a cylindrical 'cage' of thin vertical rods, the flow rate of the liquid film along the bubble surface can be increased, allowing the bubble to ascend significantly faster.