Extensional gravity-rheometry (EGR) for yield stress fluids

In order to measure the extensional rheological properties of yield stress fluids, we developed a rheometrical approach based on analysis deformations fluid extrudate flowing downward and breaking in successive elongated drops due gravity. Assuming gradients longitudinal velocity radial planes are negligible, local instantaneous strain rate is deduced from variations filament diameter each cross section, while normal computed acceleration weight material below this point. The observation profile time allows us identify solid region, which tend saturate, liquid continuously increase. A further distinguish data for pure elongational components effectively dominant so that flow curve over several decades can be deduced. For two typical fluids (emulsion clay suspension) with different internal structures, all vs obtained under these conditions fall along single master material. This elongation appears well represented by standard 3D Herschel–Bulkley model condition slightly power than simple shear used. both types, value found way very close times square root 3.