Unexpected stability of micrometer weakly viscoelastic jets

• Published in: Physics of fluids (1994) Vol. 34; no. 6
• Main Authors: Rubio, A., Vega, E. J., Gañán-Calvo, A. M., Montanero, J. M.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.06.2022
• 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
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/5.0091095

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.