Absolute instability of free-falling viscoelastic liquid jets with surfactants

Alhushaybari, Abdullah; Uddin, Jamal

doi:10.1063/1.5133627

Cited by 20 publications

(10 citation statements)

References 51 publications

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“…The theoretical framework developed here is versatile and can be readily adapted to accommodate other complex liquids, such as viscoelastic liquid films. Indeed, one can use the form of the evolution equations written in terms of the extensional stresses, τ xx , τ zz and the shear stress τ xz , and use a constitutive model appropriate for a viscoelastic liquid, e.g., Oldroyd-B model 32,33 to relate these stresses to their corresponding shear rates. This will be investigated in future.…”

Section: Discussionmentioning

confidence: 99%

Non-Newtonian and viscoplastic models of a vertically aligned thick liquid film draining due to gravity

Alahmadi

Naire

2022

Physics of Fluids

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We consider theoretically the two-dimensional flow in a vertically-aligned thick liquid film supported at the top and bottom by wire frames. The film gradually thins as the liquid drains due to gravity. We focus on investigating the influence of non-Newtonian and viscoplastic effects, such as shear thinning and yield stress, on the draining and thinning of the liquid film, important in metallic and polymeric melt films. Lubrication theory is employed to derive coupled equations for a generalised Newtonian liquid describing the evolution of the film's thickness and the extensional flow speed. We use the non-Newtonian (Power-law and Carreau) and viscoplastic (Bingham and Herschel-Bulkley) constitutive laws to describe the flow rheology. Numerical solutions combined with asymptotic solutions predict late-time power-law thinning rate of the middle section of the film. For a Newtonian liquid, a new power law thinning rate of t −2.25 is identified. This is in comparison to a thinning rate of t −2 predicted for a thin Newtonian liquid film neglecting gravity, suggesting a weak dependence on gravity for the drainage of thicker films. For a non-Newtonian and viscoplastic liquid, varying the power law index and the yield stress influences the time scale of the thinning, but has weak dependence on the late-time thinning rate relative to the Newtonian thinning rate. The shortcomings of the Power-law model are exposed when the shear rate is low and these are resolved using the Carreau model.

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Section: Discussionmentioning

confidence: 99%

Non-Newtonian and viscoplastic models of a vertically aligned thick liquid film draining due to gravity

Alahmadi

Naire

2022

Physics of Fluids

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“…We observe a similar behavior when we drape a wire flat across a surface (Movie S6). This highlights another unique feature of this system: Unlike surfactants that must diffuse to and then assemble on surfaces (7,34), an electrochemically-generated oxide deposits immediately in exposed regions and can be reversibly removed. Yet unlike solid species, the surface does not kink when bent and expands in surface area when the metal stream stops flowing.…”

Section: Resultsmentioning

confidence: 99%

“…Such jets are found both in mundane streams, such as water flowing from a faucet, as well as in important applications such as industrial sprays, fuel injection systems, polymeric fibers, inkjet nozzles, and even nuclear fission (4,5). Because the breakup of jets occurs via the Rayleigh-Plateau instability, driven by the destabilizing effects of interfacial tension, it is possible to suppress the onset of the instability by either decreasing the tension or by increasing the viscosity (6)(7)(8). Nonetheless, it has not been possible to eliminate the instability: even streams of dry granular materials -having nominally zero surface tension-can rapidly break up into clusters via the weak cohesion between the colliding particles (9).…”

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confidence: 99%

Overcoming Rayleigh–Plateau instabilities: Stabilizing and destabilizing liquid-metal streams via electrochemical oxidation

Song

Kartawira

Hillaire

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Liquids typically form droplets when exiting a nozzle. Jets––cylindrical streams of fluid—can form transiently at higher fluid velocities, yet interfacial tension rapidly drives jet breakup into droplets via the Rayleigh–Plateau instability. Liquid metal is an unlikely candidate to form stable jets since it has enormous interfacial tension and low viscosity. We report that electrochemical anodization significantly lowers the effective tension of a stream of metal, transitioning it from droplets to long (long lifetime and length) wires with 100-μm diameters without the need for high velocities. Whereas surface minimization drives Rayleigh–Plateau instabilities, these streams of metal increase in surface area when laid flat upon a surface due to the low tension. The ability to tune interfacial tension over at least three orders of magnitude using modest potential (<1 V) enables new approaches for production of metallic structures at room temperature, on-demand fluid-in-fluid structuring, and new tools for studying and controlling fluid behavior.

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“…Pipe reported a stabilizing effect of polymer addition in his experiments on viscoelastic cylindrical wakes, which is counteracted by shear thinning and a transition from convective to absolute instability at higher polymer concentrations [21]. In contrast, the linear analysis of dilute mixing layers [9] and dilute jets [22,23,24] relay a significant range of parameters where viscoelasticity was found to be destabilizing. A recent DNS study of jets [25] necessitates the use of an extra (convective) timescale to characterize the memory fading property of viscoelastic fluids.…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal linear stability of viscoelastic free shear flows: non-affine response regime

Bansal,

Ghosh,

Sircar

2021

Preprint

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We provide a detailed comparison of the two-dimensional, temporal and the spatiotemporal linearized analyses of the viscoelastic free shear flows in the limit of low to moderate Reynolds number and Elasticity number obeying four different types of stress-strain constitutive equations: Oldroyd-B, Upper Convected Maxwell, Johnson-Segalman (JS) and linear Phan-Thien Tanner (PTT). The resulting fourth-order Orr-Sommerfeld Equation is transformed into a set of six auxiliary equations that are numerically integrated via the Compound Matrix Method. The temporal stability analysis suggest (a) elastic stabilization at higher values of elasticity number (shown previously in the dilute regime [S. Sircar and D. Bansal, "Spatiotemporal linear stability of viscoelastic free shear flows: Dilute regime", Phys. Fluids 31, 084104 (2019)]), (b) a non-monotonic instability pattern at low to intermediate values of elasticity number for the JS as well as the PTT model. To comprehend the effect of elasticity, Reynolds number and viscosity on the temporal stability curves of the PTT model, we consider a fourth parameter, the centerline shear rate, ζ c . The 'JS behaviour' is recovered below a critical value of ζ c and above this critical value the PTT base stresses (relative to the JS model) is attenuated thereby explaining the stabilizing influence of elasticity. The Briggs idea of analytic continuation is deployed to classify regions of temporal stability, absolute and convective instabilities, as well as evanescent modes, and the results are compared with previously conducted experiments for Newtonian as well as viscoelastic flows past a cylinder. The phase diagrams reveal the two familiar regions of inertial turbulence modified by elasticity and elastic turbulence as well as (a recently substantiated) region of elastoinertial turbulence and the unfamiliar temporally stable region for intermediate values of Reynolds and Elasticity number.

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Absolute instability of free-falling viscoelastic liquid jets with surfactants

Cited by 20 publications

References 51 publications

Non-Newtonian and viscoplastic models of a vertically aligned thick liquid film draining due to gravity

Non-Newtonian and viscoplastic models of a vertically aligned thick liquid film draining due to gravity

Overcoming Rayleigh–Plateau instabilities: Stabilizing and destabilizing liquid-metal streams via electrochemical oxidation

Spatiotemporal linear stability of viscoelastic free shear flows: non-affine response regime

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