A generalized Ohnesorge nomogram for liquid jet breakup regimes

The present experimental study extends the Ohnesorge nomogram of liquid jet breakup regimes to viscoelastic liquids and presents a model for the jet breakup length. The experiments are carried out with water and with aqueous solutions of two different flexible polymers. The experiments rely on the visualization of the jets for identifying the breakup mechanism and for measuring the breakup length. Both the breakup mechanisms and the breakup lengths of the jets are modeled in a form allowing both Newtonian and non-Newtonian, viscoelastic liquids to be included. It is shown that, for the representation of the two classes of liquids, the dynamic viscosity to be involved must be an elongational rather than a shear viscosity. In the breakup of viscoelastic liquid jets, the elongational viscosity is a transient quantity. For breakup modeling, the terminal elongational viscosity is identified as relevant. Both the breakup mechanisms and the breakup lengths are well represented by the elongational Reynolds and Ohnesorge numbers