2-FLUID TAYLOR-COUETTE FLOW - EXPERIMENTS AND LINEAR-THEORY FOR IMMISCIBLE LIQUIDS BETWEEN COROTATING CYLINDERS

We investigate the centrifugal instability of a pair of radially strat ified immiscible liquids in the annular gap between concentric, corota ting cylinders: two-fluid Taylor-Couette flow. Experiments show that a two-layer flow with a well-defined interface and Taylor vortices in e ach phase can be obtained. The experimental results are in good agreem ent with predictions of inviscid arguments based on a two-phase extens ion of Rayleigh's criterion, as well as with detailed linear stability calculations. For a given geometry, the most stable configuration occ urs for fluids of roughly (exactly in the inviscid Limit) equal dynami c viscosities. For fluids with sufficiently low viscosity, we also exp erimentally observe another instability that is evidently the two-flui d analog of the instability of a thin film of liquid coating the insid e of a rotating drum. (C) 1998 American Institute of Physics. [S1070-6 631(98)00312-2].