Characters of surface deformation and surface wave in thermal capillary convection

In the field of fluid mechanics, free surface phenomena is one of the mostimportant physical processes. In the present research work, the surface deformation and surface wavecaused by temperature difference of sidewalls in a rectangular cavity have been investigated. Thehorizontal cross-section of the container is 52 mmx42 mm, and there is a silicon oil layer of height3.5 mm in the experimental cavity. Temperature difference between the two side walls of the cavityis increased gradually, and the flow on the liquid layer will develop from stable convection toun-stable convection. An optical diagnostic system consisting of a modified Michelson interferometerand image processor has been developed for study of the surface deformation and surface wave ofthermal capillary convection. The Fourier transformation method is used to interferometer fringeanalysis. The quantitative results of surface deformation and surface wave have been calculated froma serial of the interference fringe patterns. The characters of surface deformation and surfacewave have been obtained. They are related with temperature gradient and surface tension. Surfacedeformation is fluctuant with time, which shows the character of surface wave. The cycle period ofthe wave is 4.8 s, and the amplitudes are from 0 to 0.55 mu m The phase of the wave near the coolside of the cavity is opposite and correlative to that near the hot side. The present experimentproves that the surface wave of thermal capillary convection exists on liquid free surface, and itis wrapped in surface deformation.