Detailed measurement of fibre suspension pipe flow velocity profile

A rheometric method based on velocity profiling simultaneously by optical coherence tomography (OCT) and magnetic resonance imaging (MRI) was introduced and used in a preliminary study of the rheological and boundary layer flow properties of a microfibrillated cellulose. The two velocity profiling methods appear adequate and complementary for rheological characterization of opaque complex fluids. The MRI technique is useful in measuring the velocity profile in the interior parts of the tube, while the optical technique is capable of high-resolution measurement of the boundary layer flow close to the tube wall. The results indicate typical shear thinning behaviour in the interior part of the tube. The near wall behaviour shows existence of a slip layer related to a concentration gradient near the tube wall