Single Drop Dynamics under Shearing Flow in Systems with a Viscoelastic Phase

Abstract

In this article, we discuss the dynamics of a single drop immersed in an immiscible liquid, under an imposed shear flow. The two situations of a viscoelastic matrix with a Newtonian drop and of a viscoelastic drop in a Newtonian matrix are considered, both systems being characterized by a viscosity ratio equal to one, and by the same elasticity parameter. Experimental data are taken with a rheo‐optical computer‐assisted shearing device, allowing for drop observation from the vorticity direction of the shear flow. Data favourably compare with predictions of the recently proposed Maffettone‐Greco model, where the drop is described as a deforming ellipsoid.

Shear-induced droplet deformation: Effects of confined geometry and viscoelasticity

“…Furthermore, a stabilizing effect of N 2 against droplet breakup was predicted. Satisfactory agreement with experimental data of start-up transients [53,64], including overshoots at high Ca, and retraction were found [65]. An unexpected feature brought up by this comparison is that at high values of the Deborah number, i.e., for a sufficiently "intense" matrix elasticity, early stages of droplet dynamics are well described by the full Newtonian predictions, whereas non-Newtonian effects become evident (and are well predicted) at later times only.…”

“…The opposite case of a viscoelastic droplet in a Newtonian matrix has been experimentally investigated at a viscosity ratio of 1 by Sibillo et al [53] and Lerdwijitjarud et al [54 • ,55]. In the former study a reduced droplet deformation (although this effect is less pronounced than a Newtonian droplet in a viscoelastic matrix) and an increased orientation angle were found at a fixed Deborah number equal to 1. suppresses droplet deformation and promotes droplet orientation in agreement with experiments.…”

Influence of viscoelasticity on drop deformation and orientation in shear flow. Part 2: Dynamics

“…Matrix viscoelasticity is now known to significantly affect the droplet dynamics. First, severe overshoots may occur in the transient evolution toward a stationary state, either in startup of shear flow [11,12,13] or startup of planar extensional flow [14]. Possible causes for this overshoot are discussed in [15].…”

“…The effect of droplet viscoelasticity on transient behavior is investigated experimentally in [12,19], which show less pronounced effects than the viscoelastic matrix case. The 2D numerical simulations of [20,21] also support this conclusion.…”

A comparison of viscoelastic stress wakes for two-dimensional and three-dimensional Newtonian drop deformations in a viscoelastic matrix under shear

“…[1][2][3][4][5][6][7][8] Higher deformations require a fully numerical approach [9][10][11] which is computationally expensive because of the need to capture viscoelastic stresses that have large gradients localized next to the drop surface. At this time, a two-dimensional ͑2D͒ numerical simulation is completed on a personal computer in a few hours.…”