Experimental study of low inertia vortex rings in shear-thinning fluids

Bentata, Omar; Anne-Archard, Dominique; Brancher, Pierre

doi:10.1063/1.5048841

Cited by 19 publications

(6 citation statements)

References 37 publications

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“…57 Apart from elasticity, shear-thinning induced by the presence of polymer chains is also known to affect many features of flows, turbulent or not, from large to small scales, as described recently in several works. 62,65,66 C. Grid turbulence in polymer solution…”

Section: Articlementioning

confidence: 99%

Oscillating grid turbulence in shear-thinning polymer solutions

et al. 2019

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Oscillating grid apparatuses are well known and convenient tools for the fundamental study of turbulence and its interaction with other phenomena since they allow to generate turbulence supposedly homogeneous, isotropic, and free of mean shear. They could, in particular, be used to study turbulence and mass transfer near the interface between non-Newtonian liquids and a gas, as already done in air-water situations. Although frequently used in water and Newtonian fluids, oscillating grid turbulence (OGT) generation has yet been rarely applied and never characterized in non-Newtonian media. The present work consists of a first experimental characterization of the flow properties of shear-thinning polymer (Xanthan Gum, XG) solutions stirred by an oscillating grid. Various polymer concentrations are tested for a single grid stirring condition. The dilute and semidilute entanglement concentration regimes are considered. Liquid phase velocities are measured by Particle Image Velocimetry. The existing mean flow established in the tank is described and characterized, as well as turbulence properties (intensity, decay rate, length scales, isotropy, etc.). OGT in dilute polymer solutions induces an enhanced mean flow compared to water, a similar decay behavior with yet different decay rates, and enhanced turbulence large scales and anisotropy. In the semidilute regime of XG, turbulence and mean flows are essentially damped by viscosity. The evolution of mean flow and turbulence indicators leads to the definition of several polymer concentration subregimes, within the dilute one. Critical concentrations around 20 ppm and 50 ppm are found, comparable to drag reduction characteristic concentrations.

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Section: Articlementioning

confidence: 99%

Oscillating grid turbulence in shear-thinning polymer solutions

et al. 2019

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“…al. [9] calculates a generalized Reynolds number, which is obtained by theoretically solving for the friction factor f as a function of Re for a shear thinning fluid in a laminar pipe flow.…”

Section: Polymer Solution Characterizationmentioning

confidence: 99%

“…The reduction in ring circulation and other vortex ring parameters have been attributed to the shear thinning viscosity profile [8,9]. Palacios-Morales et.…”

Section: Elastic Effectsmentioning

confidence: 99%

“…al. [9]), the shear rates experienced by the ring is at the low shear rate end of power-law region, and quickly enter into the zero shear plateau as the ring propagates forward. Additionally, in the aforementioned studies, the viscosity of the non-Newtonian fluids is significantly larger than the water viscosity.…”

Section: Introductionmentioning

confidence: 99%

“…Bentata et al [9] studied vortex rings in shear-thinning solutions at low Reynolds number (Re ≈ 30 to 300). Their findings of the propagation properties of the vortex ring, for instance the ring velocity and ring diameter are in agreement with that obtained by Palacios [8].…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of vortex ring evolution in polymer solution

Hegde,

Sreenivas

2019

Preprint

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We have conducted experiments on the effect of polymer solutions on the formation and propagation of vortex rings. We study this effect in aqueous solution of hydrolyzed polyacrylamide (PAMH) at different concentrations. Addition of PAMH imparts shear-rate dependent viscosity and elasticity to the solvent. With increasing concentration of PAMH both the zero-shear-rate viscosity (η 0 ) and the infinite-shear-rate viscosity (η ∞ ) increase. The relaxation time also increase with the increase in concentration. We generate vortex rings using a piston-cylinder mechanism in a glass tank and measure vortex ring properties such as ring position, ring circulation, enstrophy, kinetic energy and peak vorticity using particle image velocimetry (PIV). Experiments are conducted by (1) matching impulse, and (2) matching Reynolds number. We show that, at constant impulse, vortex ring properties in PAMH solution deviate from that in Newtonian water. As the concentration of the PAMH solution increases, so too does the deviation from water. We further perform experiments in water by matching the limiting Reynolds numbers of the PAMH solution corresponding to both η 0 and η ∞ . We find that while the circulation of PAMH solutions lie between the circulation curves of the two extreme Reynolds number matched water experiments for an extended period of time, the enstrophy and peak vorticity do not. We attribute this behaviour to the modification of vorticity distribution within the core of vortex rings in PAMH solutions. We also study the effect of polymer solutions on the formation number. We find that the formation number remains the same even in polymer solutions. We also demonstrate, using planar laser induced fluorescence (PLIF), the phenomenon of ring reversal. Once the vortex ring stops, it begins to unwind and retract by translating and rotating in the opposite direction. We attribute this behaviour of ring reversal to the elastic properties of polymer solutions.

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Starting jets in non-Newtonian viscoelastic fluids: on vortex ring generation and behavior

Albagnac,

Anne-Archard

2024

Exp Fluids

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Experimental study of low inertia vortex rings in shear-thinning fluids

Cited by 19 publications

References 37 publications

Oscillating grid turbulence in shear-thinning polymer solutions

Oscillating grid turbulence in shear-thinning polymer solutions

Experimental investigation of vortex ring evolution in polymer solution

Starting jets in non-Newtonian viscoelastic fluids: on vortex ring generation and behavior

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