Abstract (Invited) |
Multi- and Single- Bubble
Sonoluminescence: Difference in Nature of Light Emission
M.Margulis (Department of
Sonochemistry, N.N. Andreyev Acoustics Institute, Moscow, Russia)
e-mail:
margulis@akin.ru
Sonoluminescence
(SL) from usual multibubble cavitation field due to electric micro- discharges
inside the cavitation bubbles at their deformations and fragmentation. Single
bubble SL is a high temperature light emission from the single spherical non
deformed bubble. Consequently, the first type of light emission has luminescent
nature, and the second one is a thermal glow. Using the results on laser
cavitation, we obtained the critical index of cavitation Kcr at that
interaction between bubbles leads to absence of high temperatures at their
compression. For water even at moderate sound intensities index of cavitation K
= 0.01- 0.9 >> Kcr = 1,2.10-3. So, even in weak multibubble systems
interaction between bubbles is substantial, practically all cavitation bubbles
are deformed and high temperatures, that could produce SL and sonochemical
reaction, are absent. At nonlinear oscillations the bubble.s forward motion
affects magnificently on radial one. Forward motion damps adiabatic bubble
.collapse. considerably, it decreases maximum temperature Tmax in 3 times (to
2800 K) and maximum radial velocity in 4 times (to 140 m.s-1). So, if heat
exchange, lose of sphericity, interaction with other bubbles and flows of
liquid are taken into account additionally, in the field of progressive sound
wave Tmax <= 1000 K.
Section
: 11