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Linear instability leading to elastic turbulence in plane Couette flow

Time: Fri 2022-11-18 10.30 - 11.30

Location: Faxén, Teknikringen 8

Participating: Miguel Beneitez (Cambridge Univ., UK)

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Abstract: It is known that a simple, Newtonian fluid may experience transition to turbulence in the presence of inertia. In contrast, viscoelastic fluids, solutions of flexible long-chain polymers, have been shown to exhibit chaotic dynamics even in the absence of inertia, entirely sustained by its elastic properties. The origin of such ‘elastic turbulence’ has often been linked to a linear instability of curved streamlines. In this talk, we present a new viscoelastic rectilinear instability in one of the most fundamental flow configurations, plane Couette flow. This instability, found in the inertialess limit, stems from a finite polymeric diffusion, caused by the molecular diffusion of the polymer chains, and relies on a novel instability mechanism. We perform the first numerical simulation of the nonlinear evolution of the associated eigenmodes and we show that it leads to self-sustained elastic turbulence in parallel flow.