Elastic turbulence in parallel shear flows: Recent progress*

Solutions of long, flexible polymer molecules are complex fluids that simultaneously exhibit fluid-like and solid-like behaviour. When subjected to external flows, dilute polymer solutions exhibit elastic turbulence - a unique, chaotic flow state absent in Newtonian fluids, like water. Unlike its Newtonian counterpart, elastic turbulence is caused by polymer molecules stretching and aligning in the flow, and can occur at vanishing inertia. While experimental realisations of elastic turbulence are well-documented, there is currently no understanding of its mechanism. 

In this talk I will review our recent progress in identifying the mechanism of elastic turbulence in pressure-driven flows through straight channels. I will present the results of large-scale direct numerical simulations of such flows and demonstrate that the transition to elastic turbulence is sub-critical, giving rise to spot-like flow structures that, further away from the transition, eventually spread throughout the domain. I will discuss the implications of these findings for the transition scenario.