On turbulent entrainment and dissipation in dilute polymer solutions

Liberzon, Alex; Holzner, Markus; Lüthi, Beat; Guala, Michele; Kinzelbach, Wolfgang

doi:10.1063/1.3097006

Cited by 19 publications

(25 citation statements)

References 30 publications

(40 reference statements)

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“…The numerical study is performed synergistically with an experimental study using Particle Image Velocimetry (PIV), following an approach similar to the one used in Liberzon et al 14 . The synergetic study is important because of two crucial aspects.…”

Section: Methodsmentioning

confidence: 99%

“…Based on our previous experience with dilute polymer solutions 4,8,14,17 , we propose to address the problem of TNTI by analyzing the growth of a localized turbulent region into a non-turbulent fluid in homogeneous solutions of dilute polymers and a Newtonian fluid.…”

Section: Introductionmentioning

confidence: 99%

“…For instance we can compare two transient cases that propagate at different rates 14 . In such case the kinetic energy in the turbulent patch is a free parameter and it hinders our ability to compare the small scale dynamics near the interface.…”

Section: Introductionmentioning

confidence: 99%

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Small scale dynamics of a shearless turbulent/non-turbulent interface in dilute polymer solutions

et al. 2017

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We study the physics of turbulent/non-turbulent interface (TNTI) of an isolated turbulent region in dilute polymer solutions and Newtonian fluid. We designed an experimental setup of a turbulent patch growing in water/dilute polymer solution, without mean shear and far from the walls. The observations from the experiments are complemented and expanded by simulations performed using a localised homogeneous forcing to generate the turbulent front and the FENE-P model for the polymer stress. The comparison, which shows that when Newtonian and viscoelastic TNTIs are fed by the same energy they behave in similar manner both in the experiments and in the simulations, permits to extend the applicability, on a qualitative basis, of single relaxation time polymer models also to turbulent/non-turbulent interfaces.From the detailed analysis offered by the numerical results, the alterations in the dynamics between strain and vorticity help understanding the mechanics of the polymer action on the TNTI without mean shear. The reduced vorticity stretching and increased vorticity compression terms are found to be due to the modified degrees of alignment between vorticity, polymer conformation tensor and rate-of-strain tensor eigenvectors observed especially near the interface. These alignments at the smallest scales of the non-Newtonian turbulent flow lead to a reduced production of enstrophy and consequently to a reduced entrainment, that in this problem are seen as reduced advancement of a turbulent region.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Small scale dynamics of a shearless turbulent/non-turbulent interface in dilute polymer solutions

et al. 2017

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“…Regarding oscillating grid turbulence in non-Newtonian liquids, only a few studies can be found in the literature (Liberzon et al 2009;Wang et al 2015Wang et al , 2016, focused on purely elastic fluids, and none of them seems to tackle the effects of variable viscosity on either the mechanisms of turbulence generation, or the mean flow and turbulence properties mapping in the whole tank. This has only been described in a recent study by Lacassagne et al (2019).…”

Section: Introductionmentioning

confidence: 99%

Flow around an oscillating grid in water and shear-thinning polymer solution at low Reynolds number

et al. 2019

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The study of turbulence in complex fluids is of great interest in many environmental and industrial applications, in which the interactions between liquid phase rheology, turbulence, and other phenomena such as mixing or heat and mass transfer have to be understood. Oscillating grid stirred tanks have been used for many purposes in research involving turbulence. However, the mechanisms of turbulence production by the oscillating grid itself have never been studied, and oscillating grid turbulence (OGT) remained undescribed in non-Newtonian, shear-thinning, dilute polymer solutions until recently (Lacassagne et al., in Phys Fluids 31(8):083,102, 2019). The aim of this paper is to study the influence of the shear-thinning property of dilute polymer solutions (DPS), such as xanthan gum (XG), on mean flow, oscillatory flows, and turbulence around an oscillating grid. Liquid phase velocity is measured by particle image velocimetry (PIV) in a vertical plane above the central grid bar. Mean, oscillatory and turbulent components of the velocity fields are deduced by triple Hussain-Reynolds decomposition based on grid phase-resolved measurements. Outside of the grid swept region, the amplitude of oscillatory fluctuations quickly become negligible compared to that of turbulent fluctuations, and the triple and classical Reynolds decomposition become equivalent. Oscillatory jets and wakes behind the grid and their interactions are visualized. Turbulent (Reynolds) and oscillatory stresses are used to evidence a modification of oscillatory flow and turbulence intensity repartition in and around the grid swept region. Energy transfer terms between mean, oscillatory and turbulent flows are estimated and used to describe turbulence production in the grid swept region. Energy is injected by the grid into the oscillatory component. In water, it is transferred to turbulence mostly inside the grid swept region. In DPS, oscillatory flow persists outside of the grid swept zone. Energy is transferred not only to turbulence , in the grid swept region, and far from the tank's walls, but also to the mean flow, leading to an enhancement of the latter. Mean flow production and enhancement mechanisms are explainable by oscillatory jet variable symmetry and intensity, and by time-and space-variable viscosity. Backward transfer from turbulence to oscillatory flow is also evidenced in DPS. Finally, using phased root mean square (rms) values of turbulent velocity fluctuations, it is shown that in water, the decay of turbulence intensity behind an oscillating grid can be related to the decay of fixed grid turbulence for specific grid positions, a result no longer valid in DPS.

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“…The dynamics of the polymer-turbulence interaction are determined by the three control parameters, namely the Reynolds number R k ; the Weissenberg number Wi which is the ratio between the polymer relaxation time s p and the smallest time scale in turbulence s g ; and the polymer concentration /. In recent years, there have been a few experimental measurements of bulk turbulence in polymer solutions (Crawford et al 2002;Liberzon et al 2005;Liberzon et al 2006;Crawford et al 2008;Liberzon et al 2009;Ouellette et al 2009), which shed new light on our understanding of turbulence-polymer interactions. However, experiments systematically exploring the full parameter space are still lacking.…”

Section: Introductionmentioning

confidence: 99%

Effects of Polymer Additive on Turbulent Bulk Flow: The Polymer Concentration Dependence

Bodenschatz

2013

Fluid-Structure-Sound Interactions and Control

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We report an experimental study of the effects of polymer additives on the turbulent bulk flow. Our results confirm that both the acceleration fluctuation a and the velocity fluctuation u of the flow are suppressed when the polymer additives are present and the suppression effect on a is much stronger. We further found that polymer additives enhance the anisotropy of the flow at small scales, but do not affect the anisotropy at large scale very much. These results are qualitatively in agreement with a recent theory which predicts that only scales smaller than a critical scale are affected by the polymer additives

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On turbulent entrainment and dissipation in dilute polymer solutions

Cited by 19 publications

References 30 publications

Small scale dynamics of a shearless turbulent/non-turbulent interface in dilute polymer solutions

Small scale dynamics of a shearless turbulent/non-turbulent interface in dilute polymer solutions

Flow around an oscillating grid in water and shear-thinning polymer solution at low Reynolds number

Effects of Polymer Additive on Turbulent Bulk Flow: The Polymer Concentration Dependence

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