Interfacial stability of multilayer viscoelastic fluids in slit and converging channel die geometries

Elastic effects in superposed fluids

“…He showed that, even if the density and viscosity of the superposed fluids match in a plane Couette flow, an elastic stratification is enough to make the interface unstable. Su and Khomami 7 found similar effects in Poiseuille flow of superposed fluids. They found that the interface between the fluids is unstable if more than half of the channel's height is filled by the fluid with lesser elasticity among the two.…”

Stability of two-layer viscoelastic plane Couette flow past a deformable solid layer

“…Apart from its practical relevance, the study of interfacial instabilities in two-layer and multilayer flows of viscoelastic fluids is also interesting from a fundamental view point, as viscoelastic fluids give rise to new mechanisms of interfacial instabilities that are absent in Newtonian fluids. Consequently, a large number of previous studies [1][2][3][4][5][6][7][8] (briefly discussed below) have focused on the theoretical understanding of two-layer and three-layer flows of viscoelastic fluids. These studies have clearly identified the parameter regimes in which interfacial instabilities occur, and have elucidated the physical mechanisms that underlie such instabilities in viscoelastic fluids.…”

Short wave instability of co-extruded elastic liquids with matched viscosities

“…Related work on this phenomenon has been performed by Su and Khomami, who have studied analytically and numerically the stability of two-layer die flow [8,9], and Renardy, who tackled the short-wave behaviour of two-layer Couette flow [7]. More recently, Laure et al [5] have studied two-and three-layer Poiseuille flow of Oldroyd-B fluids, with long to moderate wavelength perturbations, incorporating the effects of surface tension, viscosity stratification, density stratification and inertia.…”