Résultats exploitables
The aim of this project is the study of different aspects of the behaviour of fluids under microgravity conditions. Five different Research Lines have been followed:
Liquid bridges. The stability problem for an isorotating axisymmetric liquid bridge in an axial gravity field has been solved for the two typical constraints for the floating zone technique. The bifurcation problem for a weightless bridge between equal disks has been solved, and the theoretical results have been corroborated by Plateau tank experiments taking into account the combined effect of disk inequality and an axial gravity. The general stability boundaries in a wide range of Bond numbers and values of the diskradii ratio have been calculated.
Fluid layer stabilization. An experimental setup for the study of the dynamics of isothermal phase inhomogenities in liquid layers subjected to high frequency translational vibrations has been built. Systematical experimental studies of the form of surface of liquids subjected to high frequency linear vibrations have been performed.
Thermovibrational instabilities with Soret Effect. A theoretical examination of the mechanical quasi-equilibrium stability of a horizontal, binary-mixture layer with Soret effect in the presence of a high-frequency vibrational field has been performed. The boundaries of the layer are assumed to be rigid, isothermal and impermeable and the axis of vibration longitudinal. A linear stability analysis for normal modes has been done.
Boiling under microgravity conditions. Two series of similarity criteria are found to characterize a near-wall region in two regimes of nucleate boiling: developed nucleate and steady state transition.. The crisis is formulated in terms of the Reynolds number for vapor outflow from the wall. An equation for the mass flux across the liquid-vapor interface has been obtained on the base of the irreversible thermodynamics. A thermocapillary instability was found, which is described in terms of a nondimensional parametercharacterizing the ratio of the thermocapillary to the phase change. Aphenomenological model for the motion of a gas-liquid mixtute or an emulsion exposed to the thermocapillary forces and microaccelerations was formulated. The analytical and numerical investigation of one-dimensional flows for these media was fulfilled, the structure of discontinuous motions was studied. The stability conditions of a space-uniform state of an mixture and of the interface between an emulsion and a pure liquid were obtained.
Experimental facilities. An experimental setup - liquid bridge cell (LBC) - to form a small liquid bridge and examine its stability under the action of different perturbations has been developed. The setup allows to initiate axial oscillations of one of the supporting disks of the liquidbridge, rotation of both supporting disks, and axial and lateral oscillation of the whole LBC.
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