Unexpected stability of micrometer weakly viscoelastic jets

We study experimentally the stability of micrometer weakly viscoelastic jets produced with transonic flow focusing. Highly stable jets are formed when a low molecular weight polymer is added to water at a given low concentration, and the injected flow rate is reduced to its minimum value. In this ca...

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Bibliographic Details
Published in:Physics of fluids (1994) 2022-06, Vol.34 (6)
Main Authors: Rubio, A., Vega, E. J., Gañán-Calvo, A. M., Montanero, J. M.
Format: Article
Language:English
Subjects:
Breakup
Diameters
Entanglement
Flow stability
Flow velocity
Fluid dynamics
Gas pressure
Gas streams
Jets
Liquid flow
Low molecular weights
Orifices
Physics
Polymers
Relaxation time
Stress relaxation
Transonic flow
Viscoelasticity
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Summary:We study experimentally the stability of micrometer weakly viscoelastic jets produced with transonic flow focusing. Highly stable jets are formed when a low molecular weight polymer is added to water at a given low concentration, and the injected flow rate is reduced to its minimum value. In this case, the capillary instability is delayed, and the jet breakup occurs at distances from the ejector of the order of tens of thousands the jet diameter. The results indicate that the intense converging extensional flow in the ejection point builds up viscoelastic stress that does not relax in the jet even for times much longer than the polymer relaxation time. We hypothesize that the drag (shear) force exerted by the outer gas stream prevents the stress relaxation. It is also possible that partial polymer entanglement at the jet emission point contributes to this effect. We measure the jet length and the diameter at the ejector orifice and breakup point. The diameter takes values just above 2 μm at the breakup point regardless of the liquid flow rate and gas pressure.
ISSN:1070-6631
1089-7666
DOI:10.1063/5.0091095