Oscillations, Waves, and Interactions - GWDG

146 W. Lauterborn et al.
by types according to from which resonance they sprang off. Phase diagrams for
bubble oscillators can be found in Parlitz et al. [10]. Figure 5 presents a parameter
space diagram calculated with the Keller-Miksis model [13] in the (Rn, ˆpa)-parameter
space. The harmonic resonances shown form building blocks of period prolongation
that repeat with each harmonic resonance.
2.5 Single bubble in an acoustic trap
A single bubble can be trapped in the pressure antinode of a standing sound field [1].
This facilitates experiments with single bubbles considerably. The bubble oscillations
[14], the shock wave emission [15] and the light emission [16] have been studied
thereby in great detail. The simplest arrangement consists of a rectangular glass cuvette
with just one piezoelectric transducer glued to the bottom as shown in Fig. 6.
The thin wire sticking into the cuvette from the upper left side is of platinum and
serves as bubble generator via a current pulse for introducing a bubble to be trapped
into the liquid. A stably trapped bubble is to be seen by its bluish light emission. As
the bubble oscillation repeats itself with great precision each acoustic cycle, whereby
the bubble also keeps its position, the bubble can be photographed with high resolution
in time and space by use of a long distance microscope. Figure 7 shows one
cycle of a bubble oscillation driven at 24.1 kHz and taken in backlight conditions.
The time difference from one frame to the next is 500 ns. The spherical bubble shows
Figure 6. Photograph of a cubical bubble trap with the transducer glued to the bottom.
The bluish point in the middle of the upper part of the cuvette is the light emitted by a
stably oscillating bubble. Exposure time 20 min.