STABILITY OF LIQUID-LIQUID INTERFACE IN UNEVENLY ROTATING HORIZONTAL CYLINDERS

The effect of rotational velocity modulation on the shape of the interface between liquids with high contrast of viscosities and of different densities in a rapidly rotating horizontal cylinder is experimentally investigated. During rotation, the more viscous fluid with higher density is located near the lateral boundary of the cavity, and it is found that modulation of the rotation rate leads to the loss of stability of the initially axisymmetric liquid-liquid interface. The instability manifests itself in the development of a spatially periodic quasi -stationary 2D "frozen" wavy pattern on the interface. The phenomenon has a threshold character; the critical amplitude of velocity modulation depends on the rotation rate and the frequency of velocity modulation. It is shown that the appearance of the frozen waves is associated with the Kelvin-Helmholtz oscillatory instability and is accompanied by the generation of intensive vortex flows near the interphase boundary.