Local heating effect on film flow structure

Abstract

Studies of fundamental regularities governing film flow regimes are of interest for wide range of practical problems appearing in projecting and optimization of technological plants in energetic, chemical industry and other branches of industry, including space technologies. The present work is devoted to theoretical study and numerical modeling of processes in film flow of fluid on inclined surface with local heat source. Experimental researches carried out at the Institute of Thermophysics SB RAS [1] show that the effect of thermocapillarity under certain conditions can significantly influence the regime of film flow. Forming of “roller” of fluid is observed in the experiments in the area with high gradient of film surface temperature. If the temperature (or surface tension) gradient exceeds certain critical level then the periodical 3-D flow structure appears. The main quantity of fluid is gathered in periodical streams (or “fingers”). Between the streams the thickness of film decreases significantly [2]. The authors’ previous theoretical results described 2-D regime of locally heated film flow [3, 4, 5]. Those results allow us to state the following hypothesis: 2-D flow structure becomes unstable and 3-D perturbations grow as the local arrest of liquid is achieved due to thermocapillary effect (in the frame of reference moving with the heat source) [6, 7]. The results of linear stability analysis and numerical modelling are presented.