Nucleation and growth of a bubble pattern under vibrations in weightlessness
Résumé
Liquid-vapor phase transition of hydrogen was investigated during vibrations of "high" frequency = [10$\hbox$ 25.4] s-1 and "low" amplitude [0.3$\hbox$0.47] mm in a weightless environment. Gravity effects were compensated in a strong magnetic-field gradient. The experiments were performed near the liquid-vapor critical point and at liquid, slightly off-critical density. Vapor bubbles nucleate and grow in the liquid phase. During the initial stage, the mean bubble diameter, D, is lower than the viscous boundary layer thickness, $\delta$, and bubble growth is unaffected by vibrations, i.e. D ~ (time)1/3. When D > $\delta$, the bubbles and the liquid phase have different velocities and the bubble pattern orders in rows perpendicular to vibration under the influence of forces of hydrodynamic origin. An analysis in terms of Levy flight and superdiffusion gives a bubble evolution of D ~ (time)1/2, a result that compares reasonably well with the experimental data.