NUCLEAR-MAGNETIC-RESONANCE VISUALIZATION OF ANOMALOUS FLOW IN CONE-AND-PLATE RHEOMETRY

We demonstrate the use of nuclear magnetic resonance (NMR) microscopy to image the velocity distribution for fluids sheared within the gaps (4 degrees and 7 degrees) of cone-and-plate rheometers. These measurem ents employ a specially constructed rheogoniometer, which fits within the NMR probe system. While the uniform shear rate assumption is verif ied in the case of simple Newtonian and non-Newtonian fluids, a range of anomalous behavior (apparent slip, shear banding, and fracture) is observed in other systems, including wormlike surfactants, semidilute solutions of 18 MDa polyacrylamide, and dispersed silica in silicone g rease. (C) 1997 The Society of Rheology.