Experimental study of dynamics of viscous bubbly liquids in ultrasound
S.P. Sametov1,2, S.R. Gonzalez-Avila3, C.D. Ohl3, N.A. Gumerov1,4, and I.S. Akhatov5
1Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa, Russia
2Institute of Mechanics, Ufa Research Center of Russian Academy of Sciences, Ufa, Russia
3Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
4Institute for Advanced Computer Studies, University of Maryland, College Park, MD
5Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow, Russia
Self-organization of bubbles in acoustic field is a strong nonlinear effect owing to two-way field-bubbles interaction. Oscillating pressure gradient and bubbles volume give rise to averaged Bjerknes force which involves bubbles drift much slower than period of the acoustic field. As bubbles disperse and dissipate the sound, their movements lead to changes of the field. In turn this leads to manifestation of interesting nonlinear effects such as self-induced transparency  and filamentous structures formation [2, 3]. Experiments showed the formation of volume fraction with high bubbles concentration on a bubble front propagating from sound source and leaving almost clear liquid behind it .
One of important parameters controlling the process is a viscosity of liquid. Study of its influence on a velocity of the transparency wave propagation is especially important during a liquidation of microbubbles occurring during a degassing of very viscous liquids in petroleum and glass industry, for example.
In this research there are experimental results of studies which are a continuance of previous work . In the present study, the processes of viscous bubbly liquids cleaning by acoustic field are much slower, time intervals are more than 104 longer. So for present experiments a current experimental setup is modified through a fabricating of an additional cooling chamber to avoid of PZT overheating. The high-speed camera is turned into a low-speed one by adding of a signal generator to it allowing the camera to take pictures with another frequency range (0.5 – 2 frames per minute). Bubbles of two different gases (air and helium) are generated in the liquid by using the Venturi tube. As viscous medium an aqueous solution of glycerol of different viscosity is used.
Exposing the bubbly glycerol by ultrasound it is found that it leads to bubbles propagating from sound source and leaving almost clear liquid behind it. It’s also found three typical shapes of bubble front that depend of intensity of acoustic field.
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