Abstract
The interface motion of a bubble, as well as the center-of-gravity motion, is essential for deep understanding of mass transfer mechanism between gas and liquid phases in a bubble column, a gas-lift reactor, and so on. The interaction between the interface motion of each bubble and the local-scale motion of its surrounding liquid plays a role important for the mass transfer in the vicinity of its surfaces. The present paper quantitatively elucidates coupling mechanism of the center-of-gravity motion and the interface motion of an isolated single bubble in a rest water column for the purpose of a further understanding of the mass transfer mechanism. Three-dimensional visualization using high-speed video cameras equipped with microscopes and image processing were employed in the experiment and analysis. The bubble examined is 2.52mm in equivalent diameter and 747.3 in Reynolds number, in addition categorized in oblate ellipsoidal. It rises zigzag with 6.54mm in amplitude, 42.6mm in wavelength, 141.5msec in period and 297.3mm/s in velocity. As a result, the followings were confirmed: the cross-sectional contour of the bubble maintains a subround shape; the fluctuation of the curvature of the right-and-left edges of the bubbles is asymmetric, the coupling mechanism of the zigzag motion and interface motion for single rising bubble is indicative of a fascinating behavior e.g. the curvature of outside of the zigzag path is larger than that of inside, and the amplitude of the interface oscillation of outside is higher than that of inside. The interface motion is more developing at the outside of the zigzag path; a dominant oscillation of 80-90Hz is present in a bubble interface motion via Fourier transform.
