Inertio-elastic instability of non shear-banding wormlike micelles

Homogeneous polymer solutions are well known to exhibit viscoelastic flow instabilities: purely elastic when inertia is negligible and inertio-elastic otherwise. Recently, shear-banding wormlike micelle solutions were also discovered to follow a similar phenomenology. In the shear-banding regime, inertia is usually negligible so only purely elastic flows have been reported. Here, we investigate a non-shear-banding solution where inertia becomes significant, leading to flow patterns akin to the inertio-elastic regime of dilute polymer solutions. We show that the instability follows a supercritical bifurcation and we investigate the structure of the inertio-elastic vortices that develop above the onset.