Tomographic study of helical modes in bifurcating Taylor-Couette-Poiseuille flow using magnetic resonance imaging - art. no. 016319

The quantitative visualization of flow in a wide-gap annulus (radius ratio 0.5) between concentric cylinders with the inner cylinder rotating and a su perimposed axial flow reveals a novel mixed-mode state at relatively high f low rates. A fast magnetic resonance imaging sequence allows the cinematogr aphic dissection and three-dimensional reconstruction of supercritical nona xisymmetric modes in a regime where stationary helical and propagating toro idal vortices coexist. The findings shed light on symmetry-breaking instabi lities, flow pattern selection, and their consequences for hydrodynamic mix ing in a complex laminar flow that constitutes a celebrated prototype of ma ny mixing or fractionation processes.