Observations of asymmetrical flow behaviour in transitional pipe flow of yield-stress and other shear-thinning liquids

Escudier, M. P.; Poole, Robert J.; Presti, Federico Lo; Dales, C.; Nouar, Chérif; Desaubry, C.; Graham, Lachlan; Pullum, Lionel

doi:10.1016/j.jnnfm.2005.02.006

Cited by 72 publications

(64 citation statements)

References 20 publications

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“…The experimental data for U /U b at y/h = 1 can be observed to agree well with the laminar flow analytical solution until Re ≈ 800 where there is a drop off once again due to the Coriolis effect. This is in agreement with the findings of Escudier et al (2005) who obtained laminar velocity profiles in pipe flow which were slightly asymmetric for Re as low as 540 for Ek ≈ 5. Transition to turbulence can be observed to take place at Re ≈ 1250 as indicated by an increase Experiments on low-Reynolds-number turbulent flow through a square duct To determine the lowest Reynolds number for the onset of sustained turbulence, we introduce a trip rod upstream (about 238h from the measurement section).…”

Section: Experimental Studiessupporting

confidence: 93%

Experiments on low-Reynolds-number turbulent flow through a square duct

2016

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Previous experimental studies on turbulent square duct flow have focused mainly on high Reynolds numbers for which a turbulence-induced eight-vortex secondary flow pattern exists in the cross-sectional plane. More recently, direct numerical simulations (DNS) have revealed that the flow field at Reynolds numbers close to transition can be very different; the flow in this 'marginally turbulent' regime alternating between two states characterised by four vortices. In this study, we experimentally investigate the onset criteria for transition to turbulence in square ducts. In so doing, we highlight the potential importance of Coriolis effects on this process for low-Ekman-number flows. We also present experimental data on the mean flow properties and turbulence statistics in both marginally and fully turbulent flow at relatively low Reynolds numbers using laser Doppler velocimetry. Results for both flow categories show good agreement with DNS. The switching of the flow field between two flow states at marginally turbulent Reynolds numbers is confirmed by bimodal probability density functions of streamwise velocity at certain distances from the wall as well as joint probability density functions of streamwise and wall normal velocities which feature two peaks highlighting the two states.

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Section: Experimental Studiessupporting

confidence: 93%

Experiments on low-Reynolds-number turbulent flow through a square duct

2016

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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 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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“…Subsequently [2,3] it became apparent that such velocityprofile asymmetry was evident for a wide range of drag-reducing (shear-thinning and viscoelastic) polymer solutions: xanthan gum, polyacrylamide, and CMC, and also for Carbopol [3], a shearthinning, yield-stress fluid. Unless intentionally provoked, for example by an imposed asymmetric disturbance upstream [4], the time-averaged velocity profiles for fully developed transitional pipe flow of Newtonian fluids invariably are found to be axisymmetric within experimental uncertainty (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Asymmetry in transitional pipe flow of drag-reducing polymer solutions

Escudier

Rosa

Poole

2009

Journal of Non-Newtonian Fluid Mechanics

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a b s t r a c tNew experimental data are presented and discussed for fully developed pipe flow of shear-thinning, viscoelastic polymer solutions in the transitional regime between laminar and turbulent flow. The data confirm that such transitional flows exhibit significant departures from axisymmetry in contrast to the fully developed pipe flow of Newtonian fluids or both laminar and turbulent flows of such drag-reducing liquids. The azimuthal structure of the asymmetry is investigated together with its axial development and also the velocity fluctuation levels. These data do not lead to an explanation for the asymmetry but do suggest that the influence of the flow geometry both upstream and downstream can be ruled out.

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Observations of asymmetrical flow behaviour in transitional pipe flow of yield-stress and other shear-thinning liquids

Cited by 72 publications

References 20 publications

Experiments on low-Reynolds-number turbulent flow through a square duct

Experiments on low-Reynolds-number turbulent flow through a square duct

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

Asymmetry in transitional pipe flow of drag-reducing polymer solutions

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