Effects of the Vessel Diameter on Bubble-Induced Oscillation

Abstract

A unique oscillatory phenomenon was observed in a horizontal cylindrical vessel. In our previous study, we confirmed that this oscillation was caused by a bubble flow from an aeration tube located at the bottom of the vessel. Herein, to extend this research, we examined the effect of the diameter of the vessel on the oscillation induced by the bubble flow. Novel scaled-up vessels with a diameter of D=0.20 and 0.29 m were prepared. First, the occurrences of oscillation in the scaled-up vessels regardless of the scale of the vessel were confirmed. The liquid motion in the vessel was visualized to understand the mechanism of bubble-induced oscillation. The visualization showed that the upward bubble flow induced the circulating flow and the development of circulating flow caused the oscillation. The upward bubble flow oscillated and was pushed alternately by the circulating flow as if there was a spring on both sides. Second, an oscillation sensor was newly developed to automatically detect the oscillation; it could accurately measure the oscillation frequency. Using the oscillation sensor, the oscillation frequency was measured in each scale of vessel. Changes in geometry, aeration system, and height of liquid surface did not affect the oscillation frequency. It was determined to one given the diameter of the vessel. Thus, a correlation equation was proposed as a function of the diameter of the vessel. The frequency of bubble-induced oscillation was finally derived as The circumference of circulating flow, πD/4, was used as the characteristic length in the equation. The oscillation frequency estimated by the correlation equation provides good agreement with experimental results.