Extensional Viscosity Measurements for Low‐Viscosity Fluids

Fuller, Gerald G.; Cathey, Cheryl A.; Hubbard, Brent; Zebrowski, Beth E.

doi:10.1122/1.549923

Cited by 166 publications

(83 citation statements)

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“…When η e reaches the plateau value the thinning dynamic becomes linear and the elongational rateǫ diverges, indicating that η e is independent of the elongational rate as predicted by rigid rod models as well as elastic models for W i >> 1 [19]. The measured elongational viscosi-ties are in reasonable agreement with data from studies with opposing nozzles [20], fiber spinning devices [21], or values obtained by analyzing contraction flow [22] For our birefringence study we needed an estimate for the molecular weight of our sample and we used Batchelors formula [? ] for the elongational viscosity of semidiluted rigid rods to fit our data.…”

Section: A Macroscopic Measurementssupporting

confidence: 79%

Molecular configurations in the droplet detachment process of a complex liquid

2007

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We studied the microscopic polymer conformations in the droplet detachment process of an elastic semi-dilute polyelectrolytic Xanthan solution by measuring the instantaneous birefringence. As in earlier studies, we observe the suppression of the finite time singularity of the pinch-off process and the occurrence of an elastic filament. Our microscopic measurements reveal that the relatively stiff Xanthan molecules are already significantly pre-stretched to about 90 % of their final extension at the moment the filament appears. At later stages of the detachment process, we find evidence of a concentration enhancement due to the elongational flow.83.80. Rs, 47.20.Gv,

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Section: A Macroscopic Measurementssupporting

confidence: 79%

Molecular configurations in the droplet detachment process of a complex liquid

2007

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“…These fluids are also known to shear-thin (the shear viscosity decreases with increasing shear rate) and strain-harden [45,46,29,19]. The zero-shear viscosity and relaxation time of 0.16% xanthan gum mixed in 80:20 glycerol/water (with no salt) at 25…”

Section: Experimental Fluids and Apparatusmentioning

confidence: 99%

Exact solution for the extensional flow of a viscoelastic filament

et al. 2004

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We solve the free boundary problem for the dynamics of a cylindrical, axisymmetric viscoelastic filament stretching in a gravity-driven extensional flow for the Upper Convected Maxwell and Oldroyd-B constitutive models. Assuming the axial stress in the filament has a spatial dependence provides the simplest coupling of viscoelastic effects to the motion of the filament, and yields a closed system of ODEs with an exact solution for the stretch rate and filament thickness satisfied by both constitutive models. This viscoelastic solution, which is a generalization of the exact solution for Newtonian filaments, converges to the Newtonian power-law scaling as t → ∞. Based on the exact solution, we identify two regimes of dynamical behavior called the weakly-and strongly-viscoelastic limits. We compare the viscoelastic solution to measurements of the thinning filament that forms behind a falling drop for several semi-dilute (strongly-viscoelastic) polymer solutions. We find the exact solution correctly predicts the time-dependence of the filament diameter in all of the experiments. As t → ∞, observations of the filament thickness follow the Newtonian scaling 1/ √ t. The transition from viscoelastic to Newtonian scaling in the filament thickness is coupled to a stretch-to-coil transition of the polymer molecules.

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“…7a), and other strong extensional flows, such as the four roll mill and opposed jet apparatus, have been extensively investigated because of the need to develop methods for measuring the extensional viscosity of polymer solutions [46].…”

Section: Confined Flow: 2d Flow In a Cross-slotmentioning

confidence: 99%

Numerical study of the square-root conformation tensor formulation for confined and free-surface viscoelastic fluid flows

Junior

Oishi

Afonso

et al. 2016

Adv. Model. and Simul. in Eng. Sci.

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We present a numerical study of a stabilization method for computing confined and free-surface flows of highly elastic viscoelastic fluids. In this approach, the constitutive equation based on the conformation tensor, which is used to define the viscoelastic model, is modified introducing an evolution equation for the square-root conformation tensor. Both confined and free-surface flows are considered, using two different numerical codes. A finite volume method is used for confined flows and a finite difference code developed in the context of the marker-and-cell method is used for confined and free-surface flows. The implementation of the square-root formulation was performed in both numerical schemes and discussed in terms of its ability and efficiency to compute steady and transient viscoelastic fluid flows. The numerical results show that the square-root formulation performs efficiently in the tested benchmark problems at high-Weissenberg number flows, such as the lid-driven cavity flow, the flow around a confined cylinder, the cross-slot flow and the impacting drop free surface problem.

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Extensional Viscosity Measurements for Low‐Viscosity Fluids

Cited by 166 publications

References 0 publications

Molecular configurations in the droplet detachment process of a complex liquid

Molecular configurations in the droplet detachment process of a complex liquid

Exact solution for the extensional flow of a viscoelastic filament

Numerical study of the square-root conformation tensor formulation for confined and free-surface viscoelastic fluid flows

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