Experimental investigation of a two-layer shearing instability in a cylindrical Couette cell

A new experiment is presented to investigate interfacial instability between two immiscible liquids with different viscosity. Two density-matched fluids are confined between the walls of a concentric cylinder Couette cell that is aligned parallel to gravity. The resulting interface is parallel to the walls of the Couette cell and gravity. At sufficiently fast rotation rates, interfacial waves form with amplitudes that vary azimuthally and with crests parallel to gravity. Experiments and detailed results on the behavior of the system including a phase map and video stills are presented as a function of depth ratio and rotation rate. Both two-dimensional periodic wave trains and localized waves are observed. The experimental wavelength of the two-dimensional waves agree with the predictions of the Orr-Sommerfeld equation. (C) 1996 American Institute of Physics.