Viscoelastic liquid curtains: Experimental results on the flow of a falling sheet of polymer solution - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Fluid Mechanics Année : 2019

Viscoelastic liquid curtains: Experimental results on the flow of a falling sheet of polymer solution

Antoine Gaillard
  • Fonction : Auteur
  • PersonId : 850317
Cyprien Gay
Laurent Limat

Résumé

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), z being 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 gτ 2 f il , where g is gravity and τ f il is the extensional relaxation time of the liquid, beyond which 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 ((4η/ρ) 2 /g) 1/3 for Newtonian liquids of density ρ and dynamic viscosity η, which is usually small compared to the length of the curtain. The elastic length gτ 2 f il can indeed be surprisingly large when adding high molecular weight polymer molecules to a low-viscosity Newtonian solvent. By analogy with Newtonian curtains, we show that the velocity field U(z) rescales on a master curve. Besides, we show that the flow is only weakly affected by the history of polymer deformations in the die upstream of the curtain. Furthermore, investigations of the curtain stability reveal that polymer addition reduces the minimum flow rate required to maintain a continuous sheet of liquid.
Fichier principal
Vignette du fichier
Gaillard2019_Viscoelastic_curtains_HAL_good.pdf (4.88 Mo) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)

Dates et versions

hal-02343332 , version 1 (02-11-2019)
hal-02343332 , version 2 (17-05-2021)

Identifiants

Citer

Antoine Gaillard, Matthieu Roché, Sandra Lerouge, Cyprien Gay, Luc Lebon, et al.. Viscoelastic liquid curtains: Experimental results on the flow of a falling sheet of polymer solution. Journal of Fluid Mechanics, 2019, 873, pp.358-409. ⟨10.1017/jfm.2019.389⟩. ⟨hal-02343332v2⟩
89 Consultations
148 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More