Convective motions in near-critical fluids under real zero-gravity conditions

The results of processing and interpreting the data of joint Russian-French experiments for studying the heat and mass transfer in near-critical fluid s are presented. The experiments were carried out with the ALICE-1 instrume nt during an orbital flight of the Mir station from September 30 to October 2, 1995 I:I]. For such fluids with a point-like source of heat, when they are placed in the field of uncontrolled inertial accelerations of the space craft, the influence of thermovibrational and thermogravitational mechanism s of convection on the propagation of the region of optical irregularity is investigated. It is shown that, near the thermodynamic critical point, loc al heating of the medium leads to generation of either intense thermogravit ational convection or averaged vibroconvective flow, depending on the frequ ency of variations of the microaccelerations. The structure and characteris tics of discovered motions are studied. The results of numerical simulation s are presented that confirm the conclusion about a possibility of generati on of an averaged convective flow of a vibrational type by the high-frequen cy component of microaccelerations.