Development and improvement of the experimental techniques for fluid examination

Part A is motivated by preparation of the experiment JEREMI (The Japanese-European Research Experiment on Marangoni Instability) to be performed on the International Space Station (ISS). One of the objectives of the experiment is the control of the threshold of an oscillatory flow in the liquid zone by the temperature and velocity of the ambient gas. The developed set-up for a liquid bridge allows to blow gas parallel to the interface at different temperatures and investigate the effects of viscous and thermal stresses on the stability of the flow. The present study reports on isothermal experiments with moving gas and non-isothermal experiments with motionless gas when the cooling of the interface occurs due to evaporation. The discussion concerning the experimental observations is based on two sources: an interface shape measured optically and the records on thermocouples giving an indication of how temperature and frequency evolve over time.

Part B is related to ground-based studies in course of preparation and realization of the microgravity experiment DCMIX (Diffusion Coefficient in MIXtures). DCMIX project is a series of experiments aimed at measuring of the Soret coefficients in liquid mixtures on the ISS which involves a wide international group of scientists. Two experiments have been recently completed and the third one is under preparation In the course of this thesis all the aspects of the previously existing set-up for measurements of the Soret (thermal diffusion) and diffusion coefficients in binary mixtures were studied, uncertainties were identified and improvements were done to obtain reliable results. The final design has been validated by measuring coefficients in three binary benchmark mixtures and water-isopropanol. The obtained results agree well with literature data.