A velocity interferometry technique used to measure the expansion and compression phases of a sonoluminiscent microbubble
Abstract
Ultrafast compression and expansion occur in microbubbles in a variety of applications. Sonoluminiscence, i.e. the conversion of ultrasound in light, has received special attention lately and is the focus of this work. The same technique can be applied to cavitating bubbles and to the vapor micro- bubbles produced during the immersion of small red hot metallic particles (corium) in water. We have levitated bubbles of about ten microns in diameter and have focused two laser beams on the bubbles. We have computed the scattered light using Mie's theory. In the absence of a bubble, the two beams produced an interference pattern that can be approximated as light planes and dark planes. With the bubble located at the crossing points, we placed an avalanche photo-diode (APD) at the Brewster angle (approximately 80 degrees measured from the forward direction). The expansion/contraction cycle of the bubble (resonator at approximately 30 kHz, period of about 30 microseconds) produced a signal with two components: 1) a low frequency component reflecting the growth and collapse of the bubble (using an adequate callibration this information was used to estimate the bubble radius); 2) a high frequency component reflecting the rate of growth and collapse of the bubble. We have processed these data obtaining velocities as high as 125 m/s (uncertainty of about 10from the technique presented herein because in the first the particle moves as a rigid body and in the latter the velocity of the bubble is zero and one measures the interfacial velocity.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1996
- Bibcode:
- 1996APS..MAR.H3306B