Tristability in the elastic wake of confined cylinders

Polymeric flow through confined geometries is relevant in industrial applications such as enhanced oil recovery, microbial mining, groundwater remediation, and  biological processes such as drug delivery, particles and cells transport during respiration and fertilization. Large elastic stresses induced due to confined geometries can lead to elastic instability for the viscoelastic fluid flow. We have studied viscoelastic instabilities between two cylinders confined in a channel. We have discovered three distinct flow states (tristability) in the region between the cylinders induced by the elastic wake of the cylinder. Strands of high polymeric stress act as a barrier for the flow crossing these regions, which leads to flow separation and the formation of multiple flow states inside the channel. We investigate the effect of fluid rheology and cylinders’ separation on the flow instability. The strands of high polymeric stress also impact particle transport in realistic porous media.