Study on Transient Liquid Film Flow Caused by Marangoni Effect on a Small Heater

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A thin liquid film on a horizontal solid surface was heated pulsewise from beneath using a small heater. The behaviors of the transient deformation and recovery of the film surface resulting from liquid flow induced by the Marangoni effect were investigated experimentally. The conclusions obtained are as follows :(1) A significant deformation of the liquid film resulting from the rapid flow close to breaking up caused by the Marangoni effect and prompt recovery after the heating were clearly observed on and around the heater by lighting in the direction of the solid surface. As increasing heating power so that the deformation may begin at the heater temperature around the boiling point of the liquid, peculiar mist consisting of ultra-fine particles became to emerge from the thinned liquid surface.(2) The vertical displacement of the local liquid surface, which was measured using a laser focus displacement meter, showed the sequential characteristic stages. At a high heating power or a small initial liquid film thickness, the liquid film broke up on and around the heater. The displaced liquid from the heated region rushed into the next region resulting in the temporal M-shaped spatial distribution of the liquid film surface. The maximum decrease in the liquid film thickness during the deformation was well correlated with the average temperature increase of the liquid in the heated region.