Abstract
Oscillations of spark-generated bubbles are studied experimentally. In this work, an attention is paid to the time difference in the radiation of light flashes and pressure pulses from a bubble at the final stages of the first bubble contraction and the early stages of the first bubble expansion. It is found that light and pressure pulses are not radiated synchronously. In some experiments, the light flashes are radiated before the pressure pulses by a few μs and in other experiments, the light flashes are radiated later than the pressure pulses by a few μs. The time difference in the radiation of the two pulses is examined in detail in relation with the bubble size, bubble oscillation intensity, maximum value of the light flash and the width of the light flash. It is shown that the magnitude of the time differences is very weakly correlated with the bubble size, intensity of oscillation and intensity of the light flashes and that the magnitude of the time differences is only moderately correlated with the light flashes widths.
Highlights
Bubble oscillations have long been an important topic in fluid dynamics
We shall concentrate on the processes taking place in a very short interval encompassing the final stages of the bubble contraction and the early stages of the bubble expansion
To abbreviate the description of this interval, a term “subinterval in the vicinity of the minimum bubble volume” will be used in the following. This subinterval is centred on the instant tc1, when the bubble is compressed to its first minimum volume and the extent of this subinterval is about 0.5 % of the time of the first bubble oscillation To1
Summary
Bubble oscillations have long been an important topic in fluid dynamics. While they have traditionally been studied in connection with erosion damage [1], recent efforts have been aimed at medical applications such as contrast-enhancing in ultrasonic imaging [2,3,4,5,6,7]. In experiments, oscillating bubbles are generated using a wide variety of techniques These techniques encompass, e.g. laser beam focusing in the liquid [8,9,10], spark discharge in liquid [11,12,13,14,15], multiple bubbles oscillating in ultrasonic fields [16], hydrodynamic cavitation in the liquid flow [17, 18], and shock induced bubble oscillations [19]. All these techniques are used in studies of the light emission from bubbles [9, 11, 13,14,15,16,17,18,19]
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