Local Rheometry

Besides conventional rheometry based on measurements of macroscopic variables one may carry out a more sophisticated (local) rheometry. The principles of the most versatile technique which may be used for measuring the velocity profile within a non-transparent material, i.e. Magnetic Resonance Imaging (MRI) velocimetry, are reviewed. The methods for interpreting measured velocity profiles within Couette geometry in terms of the constitutive equation of the material are then discussed. Finally an alternative technique, “velocity profile reconstruction from rheometry”, which makes it possible to have a direct view of the velocity profiles over short timescales from usual rheometrical tests, is presented.