Dynamics of immiscible liquids in a rotating horizontal cylinder

• Published in: Physics of fluids (1994) 2016-11, Vol.28 (11)
• Main Authors: Kozlov, N. V., Kozlova, A. N., Shuvalova, D. A.
• Format: Article
• Language: English
• Subjects: Acceleration; Centrifugal force; Cylinders; Fluid dynamics; Gravitation; Interface stability; Liquids; Miscibility; Physics; Qualitative analysis; Rotating cylinders; Rotating liquids; Rotation
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.4966980

The dynamics of an interface between two immiscible liquids of different density is studied experimentally in a horizontal cylinder at rotation in the gravity field. Two liquids entirely fill the cavity volume, and the container is rotated sufficiently fast so that the liquids are centrifuged. The light liquid forms a column extended along the rotation axis, and the heavy liquid forms an annular layer. Under the action of gravity, the light liquid column displaces steadily along the radius, downwards in the laboratory frame. As a result, fluid oscillations in the cavity frame are excited at the interface, which lead to the generation of a steady streaming, and the fluid comes into a slow lagging rotation with respect to the cylinder walls. The dynamics of the studied system is determined by the ratio of the gravity acceleration to the centrifugal one—the dimensionless acceleration. In experiments, the system is controlled by the means of variation of the rotation rate, i.e., of the centrifugal force. At a critical value of the dimensionless acceleration the circular interface looses stability, and an azimuthal wave is excited. This leads to a strong increase in the interface differential velocity. A theoretical analysis is done based on the theory of centrifugal waves and a frequency equation is obtained. Experimental results are in good agreement with the theory at the condition of small wave amplitudes. Mechanism of steady streaming generation is analyzed based on previously published theoretical results obtained for the limiting case when the light phase is a solid cylinder. A qualitative agreement is found.