Asymmetry in transitional pipe flow of drag-reducing polymer solutions

Escudier, M. P.; Rosa, Sérgio; Poole, Robert J.

doi:10.1016/j.jnnfm.2009.04.001

Cited by 24 publications

(39 citation statements)

References 16 publications

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“…This amplitude slightly decreases when the shear-thinning character of the fluid increases. These results may be connected to a first regime found in the experiments, at intermediate Reynolds numbers, before the apparition of the puffs, where a weakly turbulent streaky structure has been found, with a dominant mode at m 0 = 1 (Escudier et al 2005(Escudier et al , 2009). The study of RPN2010 focussed on the influence of a shear-thinning rheology on EFKW m 0 = 3 waves, viewed as 'precursors' and 'support' of the puffs.…”

Section: Introductionsupporting

confidence: 61%

“…This last property is evidenced for instance in our figure 1, the figure 14 of Draad et al (1998), or the figure 2 of Escudier et al (2009). Quite probably, both phenomena, elasticity and shear-thinning, play a role in the transition to turbulence.…”

Section: Introductionsupporting

confidence: 57%

“…This modelling hypothesis can be physically justified for some fluids which show a rather weak elastic response, e.g. Xanthan Gum (Escudier et al 1999(Escudier et al , 2009). The rheological model giving the viscosity of the fluid, as a function of the shear rate, is chosen to be the Carreau model, which is a particular case of the more general Carreau-Yasuda model (Bird et al 1987).…”

Section: Introductionmentioning

confidence: 85%

“…This effect is now used in pipelines. Studying precisely the pipe flows of polymer solutions in water which exhibit drag reduction in the turbulent regime, Escudier et al (1999Escudier et al ( , 2005Escudier et al ( , 2009) also noticed a delay in the transition to turbulence, i.e., puffs set in at a larger value of the Reynolds number, Re t w , than in Newtonian fluids. Importantly, the Reynolds number used…”

Section: Introductionmentioning

confidence: 93%

“…Whereas, in Newtonian fluids, w ′ increases sharply when Re ≃ Re t = 2040, in some non-Newtonian fluids w ′ increases sharply at similar Reynolds values, but in other fluids, made of rather concentrated polymer solutions, at larger values. The largest values of Re t w are of the order of 4000 in Escudier et al (1999) (their figure 9) and Escudier et al (2005) (their figure 5b), 9000 in Escudier et al (2009) (their figure 4b). A stabilizing effect that is compatible with these results has been evidenced by Draad et al (1998) in the same range of Reynolds numbers, 2000 Re w 10000.…”

Section: Introductionmentioning

confidence: 96%

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Nonlinear waves with a threefold rotational symmetry in pipe flow: influence of a strongly shear-thinning rheology

2017

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In order to model the transition to turbulence in pipe flow of non-Newtonian fluids, the influence of a strongly shear-thinning rheology on the traveling waves with a threefold rotational symmetry of Faisst & Eckhardt (2003); is analyzed. The rheological model is Carreau's law. Besides the shear-thinning index n C , the dimensionless characteristic time λ of the fluid is considered as the main non-Newtonian control parameter. If λ = 0, the fluid is Newtonian. In the relevant limit λ → +∞, the fluid approaches a power-law behaviour. The laminar base flows are first characterized. To compute the nonlinear waves, a Petrov-Galerkin code is used, with continuation methods, starting from the Newtonian case. The axial wavenumber is optimized and the critical waves appearing at minimal values of the Reynolds number Re w based on the mean velocity and wall viscosity are characterized. As λ increases, these correspond to a constant value of the Reynolds number based on the mean velocity and viscosity. This viscosity, close to the one of the laminar flow, can be estimated analytically. Therefore the experimentally relevant critical Reynolds number Re wc can also be estimated analytically. This Reynolds number may be viewed as a lower estimate of the Reynolds number for the transition to developed turbulence. This demonstrates a quantified stabilizing effect of the shear-thinning rheology. Finally, the increase of the pressure gradient in waves, as compared to the one in the laminar flow with the same mass flux, is calculated, and a kind of 'drag reduction effect' is found.

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Section: Introductionsupporting

confidence: 61%

Section: Introductionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 96%

See 3 more Smart Citations

Nonlinear waves with a threefold rotational symmetry in pipe flow: influence of a strongly shear-thinning rheology

2017

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Direct flow simulations of thixotropic liquids in agitated tanks

Derksen

2010

Can J Chem Eng

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Simulations of transitional and turbulent flows of purely viscous thixotropic liquids in stirred tanks have been performed. The simple thixotropy model employed is based on the notion of a network in the liquid with an integrity that builds up with finite rate under quiescent conditions and breaks down under liquid deformation. We solve a transport equation for the network integrity which is two-way coupled to the latticeBoltzmann-based flow solver. The liquid's time scale characterised by the dimensionless Deborah number demonstrates to have profound impact on the level of mobilisation and the flow patterns in the mixing tanks, especially if the time scale of the liquid is of the same order as the circulation time in the tank. It also is shown to what extent increasing the impeller speed improves mobilisation.On a effectué des simulations de courants transitoires et turbulents de liquides thixotropes purement visqueux dans des cuvesà agitation. Le modèle thixotrope simple employé est fondé sur la notion d'un réseau dans le liquide avec une intégrité qui s'accumuleà un taux fini dans des conditions quiescentes et se décompose lors d'une déformation liquide. Nous avons résolu uneéquation de transport pour l'intégrité du réseau qui est couplée de façon bidirectionnelle au résolveur de flux fondé sur Lattice Boltzmann. L'échelle de temps du liquide caractérisée par le nombre de Deborah sans dimension démontre une incidence profonde sur le degré de mobilisation et les modèles de courant dans les cuves de mélange, surtout si l'échelle de temps du liquide est du même ordre que le temps de circulation dans la cuve. On démontreégalement dans quelle mesure la vitesse de l'impulseur améliore la mobilisation.

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Turbulence statistics and flow structure in fluid flow using particle image velocimetry technique: A review

Ayegba

Edomwonyi‐Otu

2020

Engineering Reports

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Particle image velocimetry (PIV) measurement technique provides an excellent opportunity for investigating instantaneous spatial structures which are not always possible with point measurements techniques like laser Doppler velocimetry. In this review, it was shown that PIV technique provides an effective means of visualizing important structures of Newtonian and drag‐reducing fluid flows. Such structures include large‐scale‐events that constitute an important portion of the Reynolds stress tensor; shear layers of drag‐reducing flows, which have been suggested to constitute the mechanism of drag reduction (DR); and near wall vortices/low speed streaks which constitute the mechanism of turbulence production. PIV investigations of turbulence statistics in Newtonian and drag‐reducing fluid flows were reviewed with the view of providing explanation to DR by additives. Results of turbulence statistics, for Newtonian fluid flow, showed that streamwise velocity fluctuations and turbulence intensity had peak values close to the wall, in a region of high mean velocity gradient, while radial fluctuating velocity and Reynolds stress tensor had peaks further from the wall and at approximately the same detachment from the wall. In single‐ and two‐phase flows in horizontal channels, the velocity profile of polymer solution, in the turbulent regime, show asymmetric behavior. This review highlighted important interfacial characteristics in gas‐liquid flows such as S‐shaped velocity profile as well as the turbulences statistics in each phase and across the interface region. Drag‐reducing agents (DRAs)‐imposed changes on turbulence statistics and flow structures were also examined. PIV studies of drag‐reducing flows showed that DRAs act to dampen wall‐normal‐, streamwise fluctuating velocity, and Reynolds stress tensor. The reduction in Reynolds stress tensor is higher than the reduction of both wall‐normal and streamwise velocity fluctuations and this discrepancy has been associated with the decorrelation of the component of fluctuating velocity. Furthermore, the addition of DRA produces a shift of the peak of wall‐normal velocity fluctuations further from the wall due to increased buffer layer thickness. DRAs do not only act to reduce drag but also to modify the flow structure. The major influence of DRAs on flow structures is seen in the reduced strength and population of vortices close to the wall, increased spacing between low‐speed streaks, reduced frequency of large‐scale events and reduced concentration of small eddies. Effect of DRAs on flow structures depends not only on the level of DR but also on the concentration and molecular weight. The effect of concentration is linked to the elastic properties of the DRA. The influence of DRA on oil‐water flows in similar to its effect on single phase water flow with regards to changes in near wall structures and turbulence statistics. A few research gaps and limitations of the PIV techniques were also highlighted.

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Asymmetry in transitional pipe flow of drag-reducing polymer solutions

Cited by 24 publications

References 16 publications

Nonlinear waves with a threefold rotational symmetry in pipe flow: influence of a strongly shear-thinning rheology

Nonlinear waves with a threefold rotational symmetry in pipe flow: influence of a strongly shear-thinning rheology

Direct flow simulations of thixotropic liquids in agitated tanks

Turbulence statistics and flow structure in fluid flow using particle image velocimetry technique: A review

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