Evaporative and convective instability in the two-layer Marangoni-Bénard
- Paper number
IAC-06-A2.4.02
- Author
Dr. Qiu-Sheng Liu, Chinese Academy of Sciences, China
- Coauthor
Dr. Rong Liu, China
- Coauthor
Mr. Qiu-Sheng Liu, Chinese Academy of Sciences, China
- Coauthor
Mr. Jia-Ping Yan, China
- Coauthor
Mrs. Shu-Ling Chen, Beijing Jiaotong University, China
- Year
2006
- Abstract
The effects of liquid evaporation on the interfacial tension-induced convection and instability are studied theoretically and experimentally in present paper. The main purpose of this investigation is to understand the mechanism of convection instability in a thin vapor-liquid layer with a mass exchange surface (interface) where exists the coupling of evaporation phenomenon and Marangoni-Bénard instability. Due to more complex thermal and dynamical mechanism at an evaporating gas-liquid interface, the modeling analysis of evaporation instability is needed to compare with pure problems of the thermal-interfacial convection instability without phase change at the interface. A systematic model of two-layer system consisting of the evaporating liquid layer and vapor-phase layer, heated from below, is studied by linear instability analyses. The thickness of both layers is finite and each layer has an infinite extension in length. The top wall is assumed as a porous medium pervious to vapor, through which the gas phase is passed in a certain velocity in order to control the evaporation flux and vapor pressure. Both non-deformable and deformable vapor-liquid interface in the perturbation state are considered, and the influence on the convection instability of the system are analyzed comparatively. Neutral stability curves of the two-layer system are presented for different cases, such as various depth ratios of two layers, evaporating mass flux, different liquid and the ratio of physical property with his own vapor phase, etc. The stability analysis shows that the evaporation not only drive evidently the temperature difference between the bottom and the evaporating interface, but also play an important role in the convective instability of the two-layer system. The influence of the deformable interface and the vapor-recoil effect on this phase-change instability problem in a quasi-enclosed two-layer system is discussed. A corresponding experimental investigation of this instability problem has been done on the ground in a cylindrical chamber heated from below. The evaporating liquids are chosen in our experiment are the FC-77 and the alcohol, respectively. In the experiment, we can adjust the flux and the pressure of the vapor by controlling the rate of the vacuum pump, which is connected with a flowmeters. The evolvement of flow pattern during the evaporation process was observed by tracer particles visualization method.
- Abstract document
- Manuscript document
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