Multibubble sonoluminescence and bubble dynamics in glycerol/water mixture system

Abstract

We investigated viscosity dependence of sonoluminescence (SL) in aqueous solutions of glycerol at acoustic frequencies of 50 and 150 kHz. The concentration dependence of SL intensity showed opposite behaviors at the two frequencies. At 50 kHz, the SL intensity increased with increasing glycerol content taking a maximum at 80% glycerol. At 150 kHz, the SL intensity decreased monotonically with increasing glycerol content. Highspeed shadowgraphy of cavitating bubbles with a frame speed of 1 Mfps demonstrated the difference in bubble dynamics at the two frequencies, and clarified the observed results of SL intensity. The increase in SL intensity at 50 kHz resulted from the increase in the number of bubbles exhibiting spherical oscillation caused by the high viscosity. The decrease in SL intensity at 150 kHz resulted from the small expansioncompression ratio of bubble oscillation caused by viscous damping. A numerical simulation of bubble oscillation supported the results.

Sonoluminescence Spectra in the First Tens of Seconds of Sonolysis of [BEPip][NTf2], at 20 kHz under Ar

“…It should be noted that a high liquid viscosity leads to the formation of peculiar bubble structures [32,33] that may also impact jetting. Ban and Choi [34] observed the formation of bubble clusters in Kr-saturated 80% glycerol (ν ≈ 100 mPa s) sonicated at 50 kHz that were similar to the clusters reported to emit Na-atom emissions and exhibited droplet injection in Xe-saturated NaCl-ethylene glycol (ν ≈ 15.5 mPa s) at 28 kHz [35].…”

“…It is interesting to compare the [BEPip][NTf 2 ] case to that of glycerol aqueous solutions because of their similar viscosities. Ban and Choi [34] observed that the 50 kHz SL intensity of glycerol solutions saturated with Kr increased from 0 to 80% glycerol, then decreased to pure glycerol, which they attributed to the too strong damping of the bubble oscillations at the high viscosity of pure glycerol (934 mPa.s). It is also at 80% glycerol that bubble clusters were reported, clusters that were correlated to the line emission in SL.…”