Heated Liquid Film Flow and Its Breakdown Caused by Marangoni Convection : The Characteristic Flow of Pure Water

Abstract

The flow characteristic of pure water partly heated on the surface was experimentally investigated using a holographic interferometer. An extremely low velocity of water surface flow compared with that of any other liquid had been previously observed. In this experiment the water surface was cleaned by sucking out the surface layer before heating. The resultant measured surface velocity was about one order of magnitude higher than that obtained without cleaning the surface and was consistent with the velocity expected by Marangoni convection, which was calculated from the temperature distribution on the water surface. The flow characteristic of pure water is not dependent on the absolute value of surface tension force, as was previously thought, but on the surface condition. If the surface is spoiled by a contaminant such as oil, dust or any other inhibiting elements, Rayleigh convection dominates the flow pattern. The effect of liquid film thickness on the flow pattern and on temperature distribution in the liquid phase is also discussed in relation to film breakdown.