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On the thinnest steady threads obtained by gravitational stretching of capillary jets
Published online by Cambridge University Press: 24 July 2013
Abstract
Experiments and global linear stability analysis are used to obtain the critical flow rate below which the highly stretched capillary jet, generated when a Newtonian liquid issues from a vertically oriented tube, is no longer steady. The theoretical description, based on the one-dimensional mass and momentum equations retaining the exact expression for the interfacial curvature, accurately predicts the onset of jet self-excited oscillations experimentally observed for wide ranges of liquid viscosity and nozzle diameter. Our analysis, which extends the work by Sauter & Buggisch (J. Fluid Mech. vol. 533, 2005, pp. 237–257), reveals the essential stabilizing role played by the axial curvature of the jet, the latter effect being especially relevant for injectors with a large diameter. Our findings allow us to conclude that, surprisingly, the size of the steady threads produced at a given distance from the exit can be reduced by increasing the nozzle diameter.
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- ©2013 Cambridge University Press
References
Rubio-Rubio et al. supplementary movie
Globally stable jet of silicone oil with a viscosity of 200 cSt, injected through a needle of 6 mm outer diameter at a constant flow rate of 3.7 ml/min, showing steady behaviour. The movie was acquired at a rate of 300 images per second, and is displayed at 30 images per second.
Rubio-Rubio et al. supplementary movie
Globally unstable jet of silicone oil with a viscosity of 200 cSt, injected through a needle of 6 mm outer diameter at a constant flow rate of 3.6 ml/min, showing the spontaneous growth of self-excited oscillations. The movie was acquired at a rate of 300 images per second, and is displayed at 30 images per second.
Rubio-Rubio et al. supplementary movie
Globally stable jet of silicone oil with a viscosity of 100 cSt, injected through a needle of 2.5 mm outer diameter at a constant flow rate of 4.8 ml/min, showing damped oscillations after an external disturbance. The movie was acquired at a rate of 300 images per second, and is displayed at 30 images per second.
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