Liquid films are encountered in space systems as well as numerous industrial processes and everyday life. The present work is a part of the preparation of the SAFIR experiment of the European Space Agency onboard the International Space Station. Wave characteristics of the water film flow over a vertical or an inclined plate with a heater have been studied. The fluorescence method was used to measure local instantaneous film thickness. In addition to measure wave characteristics eight capacitance sensors were located as a line across the flow. The process of rivulet formation in a heated film was registered. Two zones of the heat flux effect on liquid film deformation were distinguished. At low heat fluxes, the film flow is hardly deformed. At high heat fluxes the thermocapillary forces provide formation of rivulets and a thin film between them. The measured values of the distance between rivulets depend slightly on the plate inclination angle. It was found that for a positive temperature gradient along the flow, heating may increase the wave amplitude because thermocapillary forces are directed from the valley to the crest of the wave. This effect was shown in the interrivulet zone, where relative wave amplitude and Marangoni number increase with a rise of the heat flux density.
Marangoni effect on wave structure in liquid films
Marangoni-Effekt auf die Wellenstruktur in flüssigen Filmen
International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, 2 ; 18-22
Microgravity Science and Technology ; 19 , 3/4
2007
5 Seiten, 9 Bilder, 27 Quellen
Conference paper
English
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