How to extract the Newtonian viscosity from capillary breakup measurements in a filament rheometer

Abstract

The liquid filament microrheometer originally described by Bazilevsky et al. (1990) provides a simple way of extracting material parameters for Newtonian and viscoelastic fluids from measurements of the capillary breakup of a thin fluid thread. However, there is an

Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

“…When inertia is important and Oh ≪ 1, X = 0.5912 is the value most likely to be observed in an experiment 19,25,26 and hence t * 1 2 → 0.7135 as Oh → 0. When viscosity is dominant on the other hand, X = 0.7127 19,27 and t * 1 2 → 7.0522 Oh as Oh → ∞. We therefore fit the experimental data obtained for intermediate Oh values with the following rational function:…”

“…20 This permits the use of a simple stressbalance equation to extract the viscoelastic fluid stress at the necking plane from just a measurement of the radius R as a function of time t. For fluids with little or no elasticity, directly calculating the viscosity through the stress-balance has thus far been shown to be practicable again only for very viscous fluids where a cylindrical filament can form towards the final stages of breakup. 19 Thin cylindrical filaments do form close to break-up, but imaging these require the combination of ultra-fast and very high resolution photography. 21 The first of these problems was overcome in a method developed by Bhattacharjee et al, 14 wherein the liquid-bridge is created and stabilized against capillary forces initially by power input from surface acoustic radiation (Fig.…”

“…Under such conditions, a constant value of X has been shown to lead to accurate predictions. The values of X given by similarity solutions under different conditions have been summarized by McKinley and Tripathy 19 . When inertia is important and Oh ≪ 1, X = 0.5912 is the value most likely to be observed in an experiment 19,25,26 and hence t * 1 2 → 0.7135 as Oh → 0.…”

“…The values of X given by similarity solutions under different conditions have been summarized by McKinley and Tripathy 19 . When inertia is important and Oh ≪ 1, X = 0.5912 is the value most likely to be observed in an experiment 19,25,26 and hence t * 1 2 → 0.7135 as Oh → 0. When viscosity is dominant on the other hand, X = 0.7127 19,27 and t * 1 2 → 7.0522 Oh as Oh → ∞.…”

Constant force extensional rheometry of polymer solutions

“…However, they recognized that it was only possible to obtain 'apparent' transient extensional viscosities as neither the extension rateǫ = d ln L/dt nor the axial stress could directly be controlled or kept constant. As in the case of capillary breakup extensional rheometry (CABER) [24,21,30,46,1,10], this constant force pull (CFP) technique is not viewed as a true rheometer but more as an indexer for exploring and comparing the extensional behaviour of different liquids. In a capillary thinning device, a thin liquid filament of constant length is stretched beyond its Plateau stability limit and the surface tension (rather than a falling weight) provides the driving force to elongate a liquid filament.…”