Temporal instability of surfactant-laden compound jets with surface viscoelasticity

When compound jets are covered with surfactant on both interfaces, the property of those interfaces will be viscoelastic, unlike the Newtonian fluid interface. In this paper, the effects of surface viscoelasticity are principally studied through linear stability analysis and calculated using the Chebyshev spectral collocation method. Both surface elasticity and viscosity have properties to make the jet more stable, but the physical effects behind the two influencing mechanisms are different. When the inner and outer interfaces are separately covered with surfactant, the variations of surface viscoelastic parameters affect the growth rate and dominant wavenumber differently. In addition, the sensitivity of the maximum growth rate to the surface viscoelastic parameters depends on which interface the surfactant covers. A significant increase in the surface shear viscosity reduces the influence of surface elasticity on the maximum growth rate. The long-wave assumption was adopted to derive a one-dimensional dispersion equation in an algebraic form. The comparison between the simplified expression and the numerical results validated the applicability of the one-dimensional model in the vicinity of small wavenumber. (C) 2021 Elsevier Masson SAS. All rights reserved.

Automated summary

This study investigates the impact of surface viscoelasticity on the stability of compound jets and finds that surface elasticity and viscosity can stabilize the jet, but with different underlying mechanisms. Changes in surface viscoelastic parameters on different interfaces affect the growth rate and dominant wavenumber differently, with an increase in surface shear viscosity reducing the influence of surface elasticity on the maximum growth rate. The adoption of a one-dimensional dispersion equation validated the applicability of the model in the vicinity of small wavenumber.