Tuziuti Toru, Yasui Kyuichi, Sivakumar Manickam, Iida Yasuo
National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan.
Ultrasonics. 2006 Dec 22;44 Suppl 1:e357-61. doi: 10.1016/j.ultras.2006.05.002. Epub 2006 Jun 2.
The pulsation of ultrasonic cavitation bubbles at various dissolved-air concentration in a sonochemical reaction field of standing-wave type is investigated experimentally by laser-light scattering. When a thin light sheet, finer than half the wavelength of sound, is introduced into the cavitation bubbles at an antinode of sound pressure, the scattered light intensity oscillates. The peak-to-trough light intensity is correlated with the number of bubbles that contribute to the sonochemical reaction. It is shown that as the dissolved air concentration becomes higher, the weighted center of the spatial distribution of the peak-to-trough intensity tends to shift towards the liquid surface. At higher concentration of the dissolved air, a great deal of bubbles with size distribution generated due to coalescence between bubbles disturbs sound propagation to change the sound phase easily. A standing wave to trap tiny oscillating bubbles is established only at the side which is nearer to the liquid surface. Also at higher concentration, liquid flow induced by drag motion of bubbles by the action of radiation force becomes apparent and position-unstable region of bubble is enlarged from the side of sound source towards the liquid surface. Therefore, the position of oscillating bubbles active for sonochemical reaction is limited at the side which is nearer to the liquid surface at higher concentration of the dissolved air.
通过激光散射实验研究了驻波型声化学反应场中不同溶解空气浓度下超声空化气泡的脉动。当将比声波波长一半还细的薄光片引入声压波腹处的空化气泡时，散射光强度会发生振荡。峰谷光强度与对声化学反应有贡献的气泡数量相关。结果表明，随着溶解空气浓度升高，峰谷强度空间分布的加权中心倾向于向液面移动。在较高的溶解空气浓度下，由于气泡间合并产生的大量具有尺寸分布的气泡会干扰声音传播，从而容易改变声相。仅在更靠近液面的一侧形成用于捕获微小振荡气泡的驻波。同样在较高浓度下，由辐射力作用下气泡的曳引运动引起的液体流动变得明显，气泡的位置不稳定区域从声源一侧向液面扩大。因此，在较高溶解空气浓度下，对声化学反应有活性的振荡气泡位置局限于更靠近液面的一侧。
