Oscillatory and electrohydrodynamic instabilities in flow over a viscoelastic gel

A mechanism for oscillatory instability in viscoelastic cross - slot flow

Interior stagnation point flows of viscoelastic liquids arise in a wide variety of applications including extensional viscometry, polymer processing and microfluidics. Experimentally, these flows have long been known to exhibit instabilities, but the mechanisms underlying them have not previously been elucidated. We computationally demonstrate the existence of a supercritical oscillatory instab...

Instabilities in the oscillatory flow of a complex fluid.

The dynamics of a fluid in a vertical tube, subjected to an oscillatory pressure gradient, is studied experimentally for both a Newtonian and a viscoelastic shear-thinning fluid. Particle image velocimetry is used to determine the two-dimensional velocity fields in the vertical plane of the tube axis, in a range of driving amplitudes from 0.8 to 2.5 mm and of driving frequencies from 2.0 to 11....

Electrohydrodynamic Instabilities in Thin Polymer Films

Viscoelastic surface instabilities

We review three different types of viscoelastic surface instabilities: The Rayleigh – Plateau, the Saffman – Taylor and the Faraday instability. These instabilities are classical examples of hydrodynamic surface instabilities. The addition of a small amount of polymers to pure water can alter its flow behavior drastically and the type of instability may change not only quantitatively but also q...

Aspects of Electrohydrodynamic Instabilities at Polymer Interfaces

Electrospinning is emerging as a simple means of producing fibers with diameters ranging from 0.02 μm to many microns. Electrospinning, however, relies on the force generated by an electric field on the surface of a polymer solution to either enhance instabilities in a thinning jet or to rapidly elongate a jet of polymer solution form a nozzle. In this article, the fundamental physics and fluid...