RÉSUMÉ

A review of the existing literature about the formation of drops and sprays from viscoelastic liquids by single-fluid pressure atomization shows that there are not many models around for predicting the mean size of the drops. Our paper extends the finding by Liu, Z.H. and Liu, Z.B. (J. Fluid Mech., vol. 599, pp. 451–459, 2006) that liquid jets in the first wind-induced regime may be destabilized by non-axisymmetric deformations to the Rayleigh regime without any aerodynamic influence. We present models for the mean size of drops formed by the breakup of capillary axisymmetric viscoelastic liquid jets and of plane sheets. The former is based on Weber's equation for the optimum disturbance wavenumber for a Newtonian liquid jet, applying the correspondence principle. The latter is derived from the dispersion relation for a plane liquid sheet and used for predicting the Sauter-mean drop size in viscoelastic liquid sprays from pressure-swirl atomizers. Proper account for the influence from the liquid viscoelasticity on the formation of drops is essential. Influences from the molecular weight and flexibility or rigidity of the polymeric solute on the solution behavior upon deformation are represented by rheometrically accessible stress relaxation and deformation retardation times of the liquid.Mean drop sizes predicted by our models are in good agreement with experimental data.