On the thinnest steady threads obtained by gravitational stretching of capillary jets

Abstract

AbstractExperiments 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.