Viscoelastic interfacial modes in a wetting layer

Abstract

We have investigated the role of liquid elasticity in the dynamics of air-liquid interfaces during immiscible fluid displacement flows. Our experimental studies of coating flows with gravity stabilization in an eccentric cylinder geometry for both a viscous Newtonian fluid and a series of elastic Boger fluids have uncovered two new elastically driven phenomena. First, elasticity is shown to create steady, two-dimensional 'sharp interfaces' under creeping flow conditions in forward-roll coating. Digital particle image velocimetry (DPIV) and DEVSS finite element techniques are applied to investigate the effect of gravity on both the flow field and the state of polymeric stresses near the free surface. Secondly, a new class of elastically driven stable substructures is shown to form and persist along the tip, i.e. the centre stagnation line, of the two-dimensional 'sharp interfaces' even after the onset of ribbing.

Light scattering near and from interfaces using evanescent wave and ellipsometric light scattering

“…The value fits well to reference values obtained by other techniques. An EW illumination combined with Brillouin scattering detection was used by Bonn and Wegdam to study sound propagation modes in a wetting layer of a demixed binary fluid system [45]. The combination of cyclohexane and methanol formed a cyclohexane rich phase on top of a methanol rich phase.…”

Near-field Brillouin scattering as a probe of low-frequency dynamics at an interface

“…Since then, only a few investigations on the surface mode and wetting layer have been reported using Brillouin scattering [4,5]. This is because the discontinuous structure of the interface considerably affects the deformation of Brillouin scattering spectrum through the presence of the imaginary part of the wave vector of evanescent wave and also through the dispersion of phonon modes.…”