The experimental study of the periodic instability of thermocapillary convection around an air bubble
Résumé
This paper concerns an experimental study on thermocapillary convection at the interface between an air bubble and a silicone oil with a low Prandtl number. The silicone oil layer is heated from above and cooled from below in order to obtain a vertical temperature gradient. When the temperature gradient is increased and a critical value is exceeded, oscillations appear in the liquid. This oscillatory thermocapillary convection is analyzed versus the temperature gradient and the bubble aspect ratio. A non intrusive optical measurement technique based on shadow technique is developed. Three oscillations modes are observed in a vertical section of experiment cell. The systematic study shows the influence of the temperature gradient and of the bubble size on their associated characteristic frequencies. The values obtained are close to 1 Hz.