Dynamic bubbling behaviors on a micro-orifice submerged in stagnant liquid

The dynamic bubbling behaviors in a bubble column with a micro-orifice of 54 μm in diameter are studied by visual experiments. The instant images are obtained by high-speed photographic technique. With the help of image processing, a real-time tracing is applied to the bubbles formation and motion, then the evolution of the bubbling features, including bubble size, shape and velocity are discussed. The bubbles steadily grow on the micro-orifice and the linear variations of the bubble radius, aspect ratio and velocity with the height are exhibited at a low gas flow rate. With the increase in the height, the bubble velocity reduces firstly and then turns to increase, while the bubble radius and aspect ratio appears a bifurcation structure. The effect of gas flow rate on bubbling behaviors is investigated and the fast Fourier transform is adopted to analyze the periodicity of the bubbling system. A critical gas flow rate (5.4 ml/min) is found, at which the bubbling status turns from single bubbling to non-interval periodic bubbling.