Inertioelastic Poiseuille flow over a wavy surface

Streamwise boundary undulations induce spanwise vorticity in flows. In Newtonian flow, vorticity decays exponentially with distance from the undulation. However, recent theory for inertioelastic polymeric flow predicts vorticity amplification in a "critical layer" far from the site of disturbance. Here we present the first experimental evidence for the existence of such critical layers, demonstrating their measurable role in real polymeric flows with inertia. These vorticity amplification effects should be considered in all evaluations of vorticity dynamics in inertioelastic flows with streamline curvature.