Mutable bubble surface mobility in water – alcohol mixtures and its impact on bubble motion and deformation

0573992 - ÚCHP 2024 JP eng C - Konferenční příspěvek (zahraniční konf.)
Basařová, P. - Orvalho, Sandra - Crha, Jakub - Pilíková, L.
Mutable bubble surface mobility in water – alcohol mixtures and its impact on bubble motion and deformation.
Program Booklet. Kobe: -, 2023, s. 88, č. článku 68..
[International Conference on Multiphase Flow /11./. Kobe (JP), 02.04.2023-07.04.2023]
Grant CEP: GA ČR(CZ) GA19-09518S
Institucionální podpora: RVO:67985858
Klíčová slova: bubble surface mobility * bubble velocity * bubble shape * alcohol–water mixture
Obor OECD: Chemical process engineering
http://www.jsmf.gr.jp/icmf2022/doc/program_final.pdf

Various anomalies are typical for aqueous solutions of simple alcohols, with viscosity maxima and altering the bubble surface mobility being significant for multiphase systems. Two properties of alcohols appear to be key in multiphase applications: i) the amphiphilic nature of the molecule (hydrophobic and hydrophilic part), causing the preferential adsorption of molecules at the liquid–gas phase interface, thus affecting the properties of the interface, and (ii) the existence of strong hydrogen bonds, promoting the formation of structures at the molecular level (Chodzińska 2012). If the alcohol concentration increases above a certain limit (critical aggregation concentration 𝑥𝐶𝐴𝐶 ), microstructures occur that can be remotely compared to micelles in surfactant solutions. This study is focused on solutions of ethanol (𝑥𝐸𝐶𝐴𝐶 = 0.18 ) and 1-propanol (𝑥𝑃𝐶𝐴𝐶 = 0.07 ). Three regions of the hydrodynamic behaviour of spherical and ellipsoidal bubbles were observed, depending on alcohol concentration (Basařová 2022). At very low concentrations (𝑥𝐴≤ 0.005), alcohol molecules are monomolecularly dispersed and surrounded by water molecules. Alcohol behaves as a surfactant, and increasing the concentration increases the drag coefficient and decreases the bubble deformation. Upon further increase in concentration, progressive aggregation of mixture components is observed and finally, at a critical concentration, we can detect clustering. At this high concentration (𝑥𝐴 ≥ 𝑥𝐶𝐴𝐶), bubbles behave as fully mobile with a low drag coefficient. Because of the fast desorption of molecules from the bubble surface to alcohol-water clusters, neither a concentration gradient nor a surface tension gradient arises, and thus the conditions for bubble surface mobility are
fulfilled. This behavior is not affected even by the addition of different strong surfactants.
Trvalý link: https://hdl.handle.net/11104/0344367