A parametric study of droplet deformation through a microfluidic contraction

Abstract

A numerical parametric study of droplet deformation within an axisymmetric micro-fluidic contraction is performed. The simulations use a transient Volume of Fluid finite volume algorithm and cover parameter ranges representative of micro-sized liquid-liquid systems. We consider two disperse continuous viscosity ratios. When the phases have equal viscosities, the predicted droplet shapes range from short 'slugs' constrained by the contraction walls through to long thin 'filaments'. When the disperse phase viscosity is lower than that of the continuous phase, capillary waves and other instabilities develop along *

Deformation of a viscoelastic droplet passing through a microfluidic contraction

“…A staggered, uniform, structured mesh is used, with pressures located at cell centres and velocity components located at cell faces. Details of the algorithm as applied to Newtonian liquids are given in Rudman [28], as well as in the previous cylindrical contraction studies by the authors [13,14]. Preliminary versions of the method as applied to viscoelastic fluids are described in the pendant drop study of Davidson et al [10] and the cylindrical contraction study of Harvie et al [12].…”

“…To this end we have been using volume of fluid (VOF) simulations to examine how Newtonian and generalised non-Newtonian droplets deform when moving through a simple microfluidic geometry -a cylindrical 4 : 1 contraction [13][14][15]. In this study we consider a viscoelastic droplet passing through a planar contraction.…”

Simulations of viscoelastic droplet deformation through a microfluidic contraction

“…All lengths are non-dimensionalised by the radius of the inlet x * so that the contraction radius is 1/4, the contraction length is 5 and the initial droplet diameter is 1. Further details of the geometry can be found in the related Newtonian and shear thinning drop deformation studies [7,8,9]. The scaling velocity u * is taken to be the average inlet velocity, and gravitational effects are ignored.…”

“…The finite volume code, minus elastic effects, has been previously used to model the formation and subsequent 'pinch-off' of both Newtonian and generalized Newtonian pendant drops [6], the deformation of Newtonian and shear thinning drops that pass through microfluidic sized axisymmetric contractions [7,8,9], and the deformation and breakup of a continuous stream of liquid in a microfluidic 'flow focusing' device [10]. The Volume of Fluid (VOF) technique is used to track the disperse-continuous phase…”

Micro-droplet formation in non-Newtonian fluid in a microchannel

“…Analytical model is developed based on force balance which predicts well the Newtonian and power-law fluid simulation as function of Ca number. Harvie et al (2005) conducted a numerical study of droplet deformation within a micro-fluidic contraction using a VOF algorithm. The results show that the change in viscosity ratio of the two liquids leads to significantly different droplet shape and even to product instability.…”