Slender-jet equations with surface rheological effects and the Newtonian limit

We present a physically based derivation of the slender-jet equations when the jet's surface is covered with surfactant and surface rheological effects are important. We allow for the possibility that the bulk fluid and the interface may be non-Newtonian, e.g. a bulk phase that is viscoelastic and a surface phase rheology that may not follow the Boussinesq-Scriven model. Theoretical predictions deduced from slender-jet theory are compared with computational results from a fully three-dimensional axisymmetric (3DA) algorithm for a breaking surfactant covered Newtonian jet. For such jets, analytical results are shown to be in excellent accord with ones obtained from 3DA simulations.