The Time Difference in Emission of Light and Pressure Pulses From Oscillating Bubbles

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.

On the Second Light Flash Emitted From a Spark-Generated Bubble Oscillating in Water

“…Therefore, the times t 0 , t 1 and t 2 in the pressure record are delayed by about 135 µs after the times t 0 , t 1 , and t 2 in the optical record. However, as shown in [25], the instants of the liquid breakdown t 0 can be determined in both records u(t) and p(t) with a precision 0.1 µs. The pressure record can thus be shifted along the time axis so that the times t 0 in both records are identical.…”

“…The data analysed and discussed in this work are a subset of the data already presented in the works [24,25]. This means that the data were obtained using the same experimental setup.…”

“…scription of the instruments, the measuring procedure, and the nomenclature will be given here. Further details can be found in [24,25]. The freely oscillating bubbles were generated by spark discharges in a large laboratory water tank having dimensions 4 m (width), 6 m (length), and 5.5 m (depth).…”

“…In the present work, the emission of light from large spark-generated bubbles freely oscillating in water far from boundaries is studied. As mentioned in earlier works [23][24][25], the large spark-generated bubbles have many advantages that will also be exploited in this study. During the study of the light flashes radiated from these bubbles in the final stages of their first contraction and early stages of the following expansion, we occasionally observed that the first flash of light was accompanied by a slightly delayed second flash of light.…”

“…During the study of the light flashes radiated from these bubbles in the final stages of their first contraction and early stages of the following expansion, we occasionally observed that the first flash of light was accompanied by a slightly delayed second flash of light. Whereas the first flashes have been studied in detail in [24,25], in this work we want to concentrate on the second flashes. In Section 3, the time distance between the two flashes, the maximum values of these flashes, and the position of the two flashes relative to the position of the pressure pulse (and thus also with respect to an instant when the bubble is contracted to its first minimum volume) will be studied in detail.…”