Katsumi
Tsuchiya Hirofumi
Fukuta ABSTRACT Dynamics of a single bubble rising in oscillation are examined experimentally for N2 bubbles of mainly 2−3-mm diameter in the presence of a surfactant, n-butanol, in distilled water. The bubble oscillating characteristics, including local fluctuations in the rise velocity and shape, are visually traced over a limited span of vertical distance. The bubble lifetime is determined as the net period from its reaching the upper free surface to the liquid-film rupturing. The rise-path mode is found to be always zigzag if the bubble eccentricity is less than 1.5; if on the other hand the eccentricity exceeds this critical value, the rising bubble initially exhibits the spiraling mode. The amplitude of the oscillations is much larger for spiraling bubbles than for zigzagging bubbles and may varyoften being dampenedwith time, while the frequency of rise-velocity and shape fluctuations remains essentially invariant with time, especially for spiraling bubbles, on the order of 10 Hz. The extent of bubble life could critically be dominated by the phase of oscillation when the bubble has reached the free surface. For the zigzag mode, three cases of horizontal velocity contribution, i.e. zero, maximum and in-between magnitudes, are identified which result in different extents of lifetime; no classification, however, is possible for the spiral mode.
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