Extensional flow of semidilute suspensions of rod-like particles through an orifice

Abstract

This paper deals with the extensional flow of semidilute suspensions of non-Brownian rod-like particles through an orifice. The experimental setup allows simultaneously visualizations of the flow pattern and measurements of the flow rate-pressure drop relation. The flow pattern in the converging region is characterized by the appearance of a vortex ring which grows with the volume fraction of the particles and the aspect ratio. At the same time, the pressure drop experienced by the suspension as it flows through the orifice increases. The experimental results are interpreted in terms of a competition between the shear stress due to the solvent and the extensional stress generated by the particles. This interpretation is supported by the scaling of the vortex size and of the pressure drop with the volume fraction and the aspect ratio of the particles.