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Портал Begell Электронная Бибилиотека e-Книги Журналы Справочники и Сборники статей Коллекции
Interfacial Phenomena and Heat Transfer
ESCI SJR: 0.146

ISSN Печать: 2169-2785
ISSN Онлайн: 2167-857X

Open Access

Interfacial Phenomena and Heat Transfer

DOI: 10.1615/InterfacPhenomHeatTransfer.2013010211
pages 289-299

OBSERVATION OF A FALLING DROPLET WITH PH INDICATOR

Kinko Tsuji
Shimadzu Europa GmbH, Albert-Hahn-Strasse 6-10, D-47269 Duisburg, Germany
Stefan C. Muller
Institute of Experimental Physics, Otto-von-Guericke University Magdeburg, D-39106 Magdeburg, Germany

Краткое описание

The evolution of a chemical reaction on a droplet was studied by letting a drop containing the pH indicator bromothymol blue fall into alkaline liquid and, for comparison, into distilled water. For obtaining data with high spatial and temporal resolution, an ultra-high-speed camera is used. Chemical and physical properties of the evolving processes are dominated by different mechanisms in an initial phase up to 3 ms and in a later phase (3−50 ms). We find deformation of the droplet together with the chemical reaction starting along the equatorial line of the droplet. No reaction takes place at the advancing edge, where the drop impacts on the surface of the solution. Small vertical fingers emerge from the front equatorial line within 1.5 ms. Neither cuvette size nor initial height of the droplet affect these phenomena. It appears that a local chemical reaction due to the deformation of the droplet and heat diffusion play major roles during this early reactive stage. On the other hand, we find that many aspects of drop dynamics in the later phase, except flare formation, resemble those observed in previous studies, such as cavity formation and hydrodynamic fluxes influencing the drop itself, as well as the liquid surrounding it. Here, the presence of the pH indicator helps to detect dependencies on cuvette size, as well as on initial height of the droplet. The occurrence of flares may be due to the formation of a thin layer of reacted bromothymol blue the inner surface of the cavity.