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High bubble concentrations produced by ultrasounds in binary mixtures.
O Louisnard1, N Lyczko, F Espitalier
1Centre Poudres et Procédés, Ecole des Mines d'Albi-Carmaux, 81013 Albi, France. louisnar@enstimac.fr
Ultrasonics Sonochemistry
|July 10, 2001
Summary
Simultaneous ultrasound and air blowing create dense bubble clouds in aqueous solutions. These clouds, composed of ~10-micron bubbles, persist for minutes, with their formation influenced by ultrasound power and surfactant concentration.
Area of Science:
- Physical Chemistry
- Fluid Dynamics
- Acoustics
Background:
- Ultrasound and air injection can induce complex phenomena in solutions.
- Bubble dynamics are crucial in various chemical and physical processes.
Purpose of the Study:
- To investigate the formation and disappearance of concentrated bubble clouds generated by simultaneous insonification and air blowing.
- To analyze the factors influencing bubble cloud stability and characteristics.
Main Methods:
- Aqueous binary solutions (water/SDS, water/methanol, water/potassium-sulfate) were subjected to simultaneous ultrasound and air blowing.
- Computerized analysis of solution images recorded post-insonification quantified turbidity.
- Turbidity fronts were analyzed in the characteristic plane to understand bubble size distribution and dynamics.
Main Results:
- A concentrated bubble cloud rapidly filled the vessel and persisted for approximately one minute after ultrasound cessation.
- Turbidity increased with ultrasound power and sodium dodecyl sulfate (SDS) concentration.
- A rising turbidity front indicated spatial segregation of bubbles with different terminal velocities, estimated at ~10 microns.
Conclusions:
- Surface-active species adsorption likely explains bubble cloud formation and slow dissipation.
- The phenomenon's occurrence with potassium sulfate suggests mechanisms beyond simple surfactant adsorption.
- Further research is needed to fully explain the observed bubble cloud dynamics.