Disturbance spectrum of a plane fluid-fluid interface in the field of tangential high-frequency vibrations underweightlessness

The spectra of time-dependent disturbances of the equilibrium state and the stability of a plane interface between two fluid layers having different but comparable densities and being in the field of tangential high-frequency vibrations under weightlessness are investigated. Plane, spiral, and three-dimensional disturbances are considered. The cases of the same and different layer thicknesses are analyzed (in the latter case one of the layers is thicker than the other by a factor of ten). It is established that it is monotonic plane disturbances that are most hazardous. It is found that at high values of a vibration parameter growing spiral oscillatory disturbances (traveling waves) appear. With intensification of the vibrations the oscillatory disturbances vanish from the spectrum. In the case of the layers of different thicknesses it is established that the wavelength of the most hazardous disturbances is of the order of the thinner layer thickness. The experimentally observed generation of alternating strata in two-layer systems in the high-frequency vibration filed under weightlessness is attributed to the growth of disturbances having the greatest growth rate. The results obtained are quantitatively compared with the experimental data.