Sources of irreversibilities in a perfectly Axisymmetric geometry at low Reynolds numbers
Résumé
In plastic industry, a large variety of polymeric materi- als are obtained by liquid–liquid mixing. Recently, a new type of mixer (later called RMX)—based on a con- vergent/divergent unit which favors elongational flow— was developed with improved efficiency in polymer blending compared to traditional shear flow-based devices such as internal mixers or extruders. The pres- ent study aims at identifying the possible origins of the higher dispersive and distributive mixing capability of this device. An experimental study, including flow visu- alization, and numerical simulations of creeping flows induced by this original device was carried out for Newtonian, shear-thinning and viscoelastic fluids. The predictedmixing capability is based on length stretch and Lyapunov exponent methods. Calculation results show a good agreement with experiments and highlight some fundamental mixing mechanisms, such as striation, for viscoelatic fluids.