Liquid Filament Microrheometer and Some of Its Applications

Bazilevsky, A.; Entov, V. M.; Рожков, А. Н.

doi:10.1007/978-94-009-0781-2_21

Cited by 139 publications

(133 citation statements)

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“…As the filament radius decreased, the balance of forces evolved from a visco-capillary balance (corresponding to a linear decrease of the radius with time that scales with the capillary velocity 0 cap v σ η ) to an elasto-capillary balance in which the capillary pressure driving the necking process is resisted by the elastic stress in the highly elongated dumbbells. In this intermediate regime, the theory and experiments on highly viscous ideal elastic polymer solutions 22,26 show that the radius of the slender filament decreases exponentially with time until the finite extensibility of the molecules becomes important. In this final region, the extensional viscosity ( ) E η ε is high, due to the highly stretched molecules, and almost constant; the necking then becomes linear in time once more but with a characteristic velocity…”

Section: A Model For Inertio-elastic Pinchingmentioning

confidence: 99%

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

2006

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The dynamics of drop formation and pinch-off have been investigated for a series of low viscosity elastic fluids possessing similar shear viscosities, but differing substantially in elastic properties. On initial approach to the pinch region, the viscoelastic fluids all exhibit the same global necking behavior that is observed for a Newtonian fluid of equivalent shear viscosity. For these low viscosity dilute polymer solutions, inertial and capillary forces form the dominant balance in this potential flow regime, with the viscous force being negligible. The approach to the pinch point, which corresponds to the point of rupture for a Newtonian fluid, is extremely rapid in such solutions, with the sudden increase in curvature producing very large extension rates at this location. In this region the polymer molecules are significantly extended, causing a localized increase in the elastic stresses, which grow to balance the capillary pressure. This prevents the necked fluid from breaking off, as would occur in the equivalent Newtonian fluid. Alternatively, a cylindrical filament forms in which elastic stresses and capillary pressure balance, and the radius decreases exponentially with time. A (0+1)-dimensional finitely extensible nonlinear elastic dumbbell theory incorporating inertial, capillary, and elastic stresses is able to capture the basic features of the experimental observations. Before the critical “pinch time” tp, an inertial-capillary balance leads to the expected 2∕3-power scaling of the minimum radius with time: Rmin∼(tp−t)2∕3. However, the diverging deformation rate results in large molecular deformations and rapid crossover to an elastocapillary balance for times t>tp. In this region, the filament radius decreases exponentially with time Rmin∼exp[(tp−t)∕λ1], where λ1 is the characteristic time constant of the polymer molecules. Measurements of the relaxation times of polyethylene oxide solutions of varying concentrations and molecular weights obtained from high speed imaging of the rate of change of filament radius are significantly higher than the relaxation times estimated from Rouse-Zimm theory, even though the solutions are within the dilute concentration region as determined using intrinsic viscosity measurements. The effective relaxation times exhibit the expected scaling with molecular weight but with an additional dependence on the concentration of the polymer in solution. This is consistent with the expectation that the polymer molecules are in fact highly extended during the approach to the pinch region (i.e., prior to the elastocapillary filament thinning regime) and subsequently as the filament is formed they are further extended by filament stretching at a constant rate until full extension of the polymer coil is achieved. In this highly extended state, intermolecular interactions become significant, producing relaxation times far above theoretical predictions for dilute polymer solutions under equilibrium conditions.

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Section: A Model For Inertio-elastic Pinchingmentioning

confidence: 99%

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

2006

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“…High molecular mass polymer solutions are prone to develop thin liquid filaments, such as those seen between the beads in figure 1. This enables the determination of a longest relaxation time λ for the solution from the direct observation of the capillary thinning kinetics of thin liquid filaments, as discussed in Bazilevskii et al (1990aBazilevskii et al ( , 2001; Entov & Hinch (1997);McKinley & Tripathi (2000); Anna & McKinley (2001) and Clasen, Plog, Kulicke, Owens, Macosko, Scriven, Verani & McKinley (2006b were carried out using an extensional rheometer (CABER-1, Cambridge Polymer Group) described in Braithwaite & Spiegelberg (2001).…”

Section: Fluid Propertiesmentioning

confidence: 99%

“…Eventually the filament breaks in finite time once the finite extensibility limit of the polymer chains is reached. According to the theory presented elsewhere (Bazilevskii et al (1990a); Entov & Hinch (1997); Anna & McKinley (2001); Bazilevskii et al (2001); Plog et al (2005) and Clasen et al (2006a)), the longest relaxation time can then be evaluated as:…”

Section: Fluid Propertiesmentioning

confidence: 99%

‘Gobbling drops’: the jetting–dripping transition in flows of polymer solutions

et al. 2009

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This paper discusses the breakup of capillary jets of dilute polymer solutions and the dynamics associated with the transition from dripping to jetting. High speed digital video imaging reveals a new scenario of transition and breakup via periodic growth and detachment of large terminal drops. The underlying mechanism is discussed and a basic theory for the mechanism of breakup is also presented. The dynamics of the terminal drop growth and trajectory prove to be governed primarily by mass and momentum balances involving capillary, gravity and inertial forces, whilst the drop detachment event is controlled by the kinetics of the thinning process in the viscoelastic ligaments that connect the drops. This thinning process of the ligaments that are subjected to a constant axial force is driven by surface tension and resisted by the viscoelasticity of the dissolved polymeric molecules. Analysis of this transition provides a new experimental method to probe the rheological properties of solutions when minute concentrations of macromolecules have been added.

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“…Following the original analysis by Entov and coworkers [9,10,11], capillary thinning rheometry has become a standard technique for rapidly measuring the extensional properties of a wide range of viscoelastic fluids, including polymer solutions. The Capillary Breakup Extensional Rheometer (CaBER) is a commercially available instrument that is frequently used to perform these types of measurements.…”

Section: Introductionmentioning

confidence: 99%

An analytic solution for capillary thinning and breakup of FENE-P fluids

Wagner

Bourouiba

McKinley

2015

Journal of Non-Newtonian Fluid Mechanics

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The FENE-P model of a fluid is particularly suitable for describing the rheology of dilute polymer solutions (Newtonian solvents containing small amounts of dissolved polymer) as a result of its ability to capture nonlinear effects arising from the finite extensibility of the polymer chains. In extensional flows, these polymer solutions exhibit dramatically different behaviour from the corresponding Newtonian solvents alone, notably through the creation of persistent filaments when stretched. By using the technique of capillary thinning to study the dynamics of the thinning process of these filaments, the transient extensional rheology of the fluid can be characterized. We show that under conditions of uniaxial elongational flow, a composite analytic solution can be developed to predict the time evolution of the radius of the filament. Furthermore we derive an analytic expression for the finite time to breakup of the fluid filaments. This breakup time agrees very well with results obtained from full numerical simulations, and both numerics and theory predict an increase in the time to breakup as the finite extensibility parameter b, related to the molecular weight of the polymer, is increased. As b → ∞, the results converge to an asymptotic result for the breakup time which shows that the breakup time grows as t break ∼ ln(M W ), where M W is the molecular weight of the dilute polymer solution.

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Liquid Filament Microrheometer and Some of Its Applications

Cited by 139 publications

References 1 publication

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration

‘Gobbling drops’: the jetting–dripping transition in flows of polymer solutions

An analytic solution for capillary thinning and breakup of FENE-P fluids

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