Viscoelastic instability in an asymmetric geometry

Viscoelastic flow through porous media is important in industrial applications such as enhanced oil recovery (EOR), microbial mining, and groundwater remediation. It is also relevant in biological processes such as drug delivery, infectious biofilm formation, and transport during respiration and fertilization. The porous medium is highly disordered and viscoelastic instability-induced flow states at the pore-scale regulate the transport in porous media. In the present study, we systematically explore the effect of geometrical asymmetry on pore-scale viscoelastic instability. The asymmetric geometry used in the present study consists of two cylinders confined inside a channel, where the front cylinder is located on the centerline of the channel and the rear cylinder is situated off-center of the channel. The geometrical asymmetry facilitates asymmetric flow around both cylinders. An eddy also appears in the region between the cylinders at intermediate Weissenberg numbers, where the Weissenberg number characterizes the relative importance of elastic and viscous forces in viscoelastic flows. We further explore the effect of the strength of geometrical asymmetry and fluid rheological properties on flow asymmetry and eddy formation.