scholarly journals Oscillating grid generating turbulence near gas-liquid interfaces in shear-thinning dilute polymer solutions

2020 ◽  
Vol 5 (3) ◽  
Author(s):  
T. Lacassagne ◽  
S. Simoëns ◽  
M. EL Hajem ◽  
J.-Y. Champagne
Keyword(s):  
Polymer Solutions ◽  
Shear Thinning ◽  
Liquid Interfaces ◽  
Dilute Polymer Solutions ◽  
Oscillating Grid

Surface-tension-driven breakup of viscoelastic liquid threads

1982 ◽  
Vol 120 ◽  
pp. 245-266 ◽  
Author(s):  
Simon L. Goren ◽  
Moshe Gottlieb
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Polymer Solutions ◽  
Small Diameter ◽  
Shear Thinning ◽  
Prior History ◽  
Axial Tension ◽  
Dilute Polymer Solutions ◽  
Linearized Stability ◽  
Newtonian Liquids

A linearized stability analysis is carried out for the breakup of small-diameter liquid filaments of dilute polymer solutions into droplets. Oldroyd's 8-constant model expressed in a corotational reference frame is used as the rheological equation of state. The crucial idea in this theory is the recognition that the liquid may be subject to an unrelaxed axial tension due to its prior history. If the tension is zero, the present analysis predicts that jets of shear-thinning liquids are less stable than comparable jets of Newtonian liquids; this is in agreement with previous analyses. However, when the axial tension is not zero, and provided the stress relaxation time constant is sufficiently large, the new theory predicts that the axial elastic tension can be a significant stabilizing influence. With reasonable values for the tension and stress relaxation time the theory explains the great stability observed for jets of some shear- thinning, dilute polymer solutions. The theory explains why drops produced from jets of such liquids are larger than drops from corresponding Newtonian liquids. The theory also appears capable of explaining the sudden appearance of irregularly spaced bulges on jets after long distances of t,ravel with little amplification of disturbances.

Shear thinning in dilute polymer solutions

2006 ◽  
Vol 125 (19) ◽  
pp. 194906 ◽  
Author(s):  
J. F. Ryder ◽  
J. M. Yeomans
Keyword(s):  
Polymer Solutions ◽  
Shear Thinning ◽  
Dilute Polymer Solutions

scholarly journals Oscillating grid turbulence in shear-thinning polymer solutions

2019 ◽  
Vol 31 (8) ◽  
pp. 083102 ◽  
Author(s):  
T. Lacassagne ◽  
S. Simoëns ◽  
M. EL Hajem ◽  
A. Lyon ◽  
J.-Y. Champagne
Keyword(s):  
Polymer Solutions ◽  
Shear Thinning ◽  
Grid Turbulence ◽  
Oscillating Grid

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

2019 ◽  
Vol 61 (1) ◽  
Author(s):  
Tom Lacassagne ◽  
Adrien Lyon ◽  
Serge Simoëns ◽  
Mahmoud El Hajem ◽  
Jean-Yves Champagne
Keyword(s):  
Liquid Phase ◽  
Turbulence Intensity ◽  
Oscillatory Flow ◽  
Shear Thinning ◽  
Grid Turbulence ◽  
Mean Flow ◽  
Dilute Polymer Solutions ◽  
Reynolds Decomposition ◽  
Turbulence Production ◽  
Oscillating Grid

Abstract 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. Graphic abstract

On Shear Thinning in Dilute Polymer Solutions

1989 ◽  
Vol 177 ◽  
Author(s):  
Yitzhak Rabin ◽  
H. C. Öttinger ◽  
K. Kawasaki
Keyword(s):  
Shear Rate ◽  
Polymer Solutions ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Weissenberg Number ◽  
Dilute Polymer Solutions

ABSTRACTWhile recent remrmalization group studies predict shear thickening in the limit of large Weissenberg numbers, scaling theories predict shear thinning. The ocntroversy is related to the question whether the Weissenberg number or the shear rate should be kept fixed when taking the limit of infinitely long polymers.

On the mechanism of drag reduction in dilute polymer solutions

1996 ◽  
Vol 55 (4) ◽  
pp. 289-295 ◽  
Author(s):  
K. Hoyer ◽  
A. Gyr ◽  
A. Tsinober
Keyword(s):  
Drag Reduction ◽  
Polymer Solutions ◽  
Dilute Polymer Solutions
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