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Flow instabilities and turbulence in viscoelastic fluids
The aim of the workshop is to understand physical mechanisms driving purely elastic flow instabilities and turbulence in dilute polymer solutions. We would like to bring together researchers working on various systems and geometries and try to formulate a unifying picture of the transition to purely elastic turbulence in polymeric flows.
We would like to specifically address the following directions:
· Coherent structures. Recently, our understanding of the transition to Newtonian turbulence in parallel shear flows has changed with the discovery of exact solutions of the Navier-Stokes equations – coherent structures. At least close to the transition onset, the turbulent dynamics is organised by these coherent structures and is, in some sense, low-dimensional. An intriguing possibility would be if purely elastic turbulence has the same nature.
· Stability of viscoelastic parallel shear flows. It has been proposed that in viscoelastic parallel shear flows, like flow in a pipe of channel flow, there exists a non-linear instability leading directly to a chaotic flow. The question whether this instability exists is still unsettled.
· Status of the relation between curved streamlines and linear instability
· Relation between elastic turbulence and drag-reduction
· Instabilities in extensional flows. Recent experiments show that extensional flows of dilute polymer solutions are also unstable. Presently the nature and the mechanism of this instability remains unclear.