WHAT CAN WE LEARN ABOUT TRANSPORT PHENOMENA FROM A STUDY OF CRITICAL FLUIDS IN MICROGRAVITY

Pure fluids and liquid mixtures near their critical point (gas-liquid, liquid-liquid) happen to be good candidates to put in evidence the mechanisms that are most often hidden on Earth by gravity-induced convective phenomena. The properties of fluids in their critical region can indeed be put under a universal form (scaling laws) within a large-domain of temperature and pressure. We discuss two recent results that were obtained during a sounding rocket flight. One of them is concerned with the observation of a very rapid thermalization process due to the expansion of a boundary layer ("Piston Effect") and the other involves the growth of domains during phase separation that appears to be dominated by capillary flows.