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Viscoelastic liquid curtains: Experimental results on the flow of a falling sheet of polymer solution
- Source :
- Journal of Fluid Mechanics, Journal of Fluid Mechanics, Cambridge University Press (CUP), 2019, 873, pp.358-409. ⟨10.1017/jfm.2019.389⟩
- Publication Year :
- 2019
- Publisher :
- HAL CCSD, 2019.
-
Abstract
- We experimentally investigate the extensional flow of a sheet – or curtain – of viscoelastic liquid falling freely from a slot at constant flow rate under gravity. Extruded liquids are aqueous solutions of flexible polyethylene oxide (PEO) and of semi-rigid partially hydrolysed polyacrylamide (HPAM) with low shear viscosities. Velocimetry measurements reveal that the mean velocity field $U(z)$ (where $z$ is the distance from the slot exit) does not reduce to a free fall. More precisely, we show that the liquid falls initially with sub-gravitational accelerations up to a distance from the slot which scales as $g\unicode[STIX]{x1D70F}_{fil}^{2}$ (where $g$ is gravity and $\unicode[STIX]{x1D70F}_{fil}$ is the extensional relaxation time of the liquid) due to the stretching of polymer molecules. Beyond this elastic length, inertia dominates and the local acceleration reaches the asymptotic free-fall value $g$. The length of the sub-gravitational part of the curtain is shown to be much larger than the equivalent viscous length $((4\unicode[STIX]{x1D702}/\unicode[STIX]{x1D70C})^{2}/g)^{1/3}$ for Newtonian liquids of density $\unicode[STIX]{x1D70C}$ and dynamic viscosity $\unicode[STIX]{x1D702}$ which is usually small compared to the curtain length. By analogy with Newtonian curtains, we show that the velocity field $U(z)$ rescales on a master curve. Besides, the flow is shown to be only weakly affected by the history of polymer deformations in the die upstream of the curtain. Furthermore, investigations on the curtain stability reveal that polymer addition reduces the minimum flow rate required to maintain a continuous sheet of liquid.
- Subjects :
- Gravity (chemistry)
Materials science
business.product_category
Flow (psychology)
Polyacrylamide
02 engineering and technology
01 natural sciences
Viscoelasticity
010305 fluids & plasmas
[SPI.MAT]Engineering Sciences [physics]/Materials
Physics::Fluid Dynamics
chemistry.chemical_compound
[SPI]Engineering Sciences [physics]
0103 physical sciences
[NLIN]Nonlinear Sciences [physics]
Composite material
[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]
[NLIN.NLIN-AO]Nonlinear Sciences [physics]/Adaptation and Self-Organizing Systems [nlin.AO]
chemistry.chemical_classification
[PHYS]Physics [physics]
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph]
Mechanical Engineering
[SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment
Polymer
[PHYS.MECA]Physics [physics]/Mechanics [physics]
Velocimetry
021001 nanoscience & nanotechnology
Condensed Matter Physics
Shear (sheet metal)
Condensed Matter::Soft Condensed Matter
chemistry
Mechanics of Materials
Die (manufacturing)
0210 nano-technology
business
[PHYS.COND.CM-SCM]Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft]
Subjects
Details
- Language :
- English
- ISSN :
- 00221120 and 14697645
- Database :
- OpenAIRE
- Journal :
- Journal of Fluid Mechanics, Journal of Fluid Mechanics, Cambridge University Press (CUP), 2019, 873, pp.358-409. ⟨10.1017/jfm.2019.389⟩
- Accession number :
- edsair.doi.dedup.....3fefe9be907c4dc282e0cda0c0cee1c4
- Full Text :
- https://doi.org/10.1017/jfm.2019.389⟩